Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
FORMULATION AND EVALUATION OF A CONTROLLED RELEASE ORAL HYPOGLYCAEMIC TABLET
Thesis submitted in
the partial fulfilment for the award of
Degree of Doctor of Philosophy
in Pharmaceutical Sciences
By
Deepu S
(Reg. No. J863600003)
VINAYAKA MISSION UNIVERSITY
SALEM, TAMILANDU, INDIA.
JANUARY 2015
I
VINAYAKA MISSION UNIVERSITY, SALEM
CERTIFICATE BY THE GUIDE
I, Dr. (Sr.) Molly Mathew, certify that the thesis entitled “Formulation
and evaluation of a controlled release oral hypoglycemic tablet” submitted
for the degree of Doctor of Philosophy by Mr. Deepu S, is the record of
research work carried out by him during the period from July 2008 to July
2014 under my guidance and supervision and that this work has not
formed the basis for the award of any degree, diploma, associate-ship,
fellowship or other titles in this University or any other University or
Institutions of higher learning.
Place: Kasaragod
Date:
Dr. (Sr). Molly Mathew, B.Sc, M.Pharm, Ph.D Principal, Malik Deenar College of Pharmacy, Seenthangoli, Bela Post, Kasaragod-671 321, Kerala, India.
II
VINAYAKA MISSION UNIVERSITY, SALEM
CERTIFICATE BY THE CO-GUIDE
I, Dr. K L Senthilkumar, certify that the thesis entitled “Formulation and
evaluation of a controlled release oral hypoglycemic tablet” submitted for the
degree of Doctor of Philosophy by Mr. Deepu S, is the record of research
work carried out by him during the period from July 2008 to July 2014 under
my guidance and supervision and that this work has not formed the basis
for the award of any degree, diploma, associate-ship, fellowship or other
titles in this University or any other University or Institutions of higher
learning.
Place: Dharmapuri
Date:
Dr. K L Senthilkumar Principal, Padmavathy college of Pharmacy, Krishnagiri main road, Periyanahalli, Dharmapuri - 635205 Tamil Nadu.
III
VINAYAKA MISSION UNIVERSITY, SALEM
DECLARATION
I, Mr. Deepu S, declare that the thesis entitled “Formulation and
evaluation of a controlled release oral hypoglycaemic tablet” submitted by me
for the degree of Doctor of Philosophy is the record of research work carried out
by me during the period from July 2008 to July 2014 under the guidance of Dr.
(Sr). Molly Mathew and co-guidance of Dr. K L Senthilkumar and, has not formed
the basis for the award of any degree, diploma, associate-ship, fellowship or
other titles in this University or any other University or Institutions of higher
learning.
Place: Trivandrum Date:
Mr. Deepu S Mar Dioscorus College of pharmacy Mount Hermon, Alathara, Sreekariyam, Trivandrum-695017 Kerala, India.
IV
ACKNOWLEDGEMENT
I humble myself before my God the Almighty for the countless blessings
showered upon me all through my life and for giving me the ultimate guidance
for the successful completion of the dissertation.
This thesis would not have been materialized without the immeasurable
help from many people who gave their support in different ways. To them I would
like to convey the heartfelt gratitude and sincere appreciation.
It is with great pleasure that I acknowledge my esteemed guide Dr. (Sr).
Molly Mathew, Principal, Malik Deenar College of Pharmacy, Kasaragod,
Kerala for her invaluable guidance, effective criticism and for creating an
environment so conducive for learning. She has been instrumental for the
smooth flow of this research work. This period has been an enriching experience
of working under her guidance. I thank her whole heartedly.
I pay my profound gratefulness and indebtedness to Dr. K. Rajendran,
Dean–research of Vinayaka Missions University, Salem for his timely support. I
express my sincere thanks to my Co-guide Dr. K L Senthilkumar, Principal,
Padmavathy College of pharmacy, Dharmapuri, for his valuable suggestion and
support to accomplish this research work.
I gratefully acknowledge my dearest Friend, Mrs. Shamna.M.S, who has
shared her time, patience and care, with all the full support and encouragement,
all of which have contributed to the successful completion of the thesis work.
Without her this thesis would not have been a reality. I would like to extend my
deep sense of gratitude to Mr. Elayaraja R, Scientist, Dr Reddy’s Laboratories,
V
who had kindly provided me the gift sample required for my work and for his
advice, discussion, and help throughout the work.
I extend my gratitude to management of St. Joseph College of
Pharmacy for helping me to carry out the pharmaceutical and evaluation
studies.
I am grateful to Prof. Dr. M. A. Kuriachan, Principal, Mar Dioscorus
College of Pharmacy, Trivandrum, for his encouragement and advice.
I take this opportunity to thank the Management of Mar Dioscorus
College of Pharmacy for the support to accomplish this research work.
I owe my deepest gratitude to my colleagues Mr. Ganesh Sanker S, Mrs.
Sivazeena T. S, Mr. Praveenraj. R, and Sujith S Nair for helping me to get
through the difficult times and for all the emotional support, entertainment and
caring they provided.
My deepest love and gratitude go to my dear parents, family and my child,
Neha for their unflagging love, prayers and support throughout my life, all of
which helped me to complete my dissertation successfully.
DEEPU S
VI
CONTENTS
LIST OF FIGURES .................................................................................................... XI
LIST OF TABLES ................................................................................................... XIII LIST OF ABBREVATIONS AND SYMBOLS ........................................................... XV
1. INTRODUCTION ................................................................................................ 1
1.1. Oral controlled drug delivery system .............................................................. 2 1.2. Challenges in controlled release formulations ................................................ 4 1.3. Rationale for designing controlled drug delivery ............................................. 5 1.4. Matrix tablets .................................................................................................. 6 1.5. Polymers used in matrix tablets ..................................................................... 7 1.6. Classification of matrix tablets ........................................................................ 9 1.6.1. Hydrophilic matrix tablet ............................................................................ 10
1.6.2. Hydrophobic matrix tablets ........................................................................ 11
1.7. Mechanism of drug release from matrix tablet ............................................. 12 1.8. Bimodal Release .......................................................................................... 15 1.9. Boundaries of gel layer and relevant fronts .................................................. 17 1.10. Swellable matrix tablets as drug delivery systems .................................... 18 1.11. Factors affecting drug release from a matrix system ................................ 19 1.12. Biological factors influencing release from matrix tablets .......................... 23 1.13. Physicochemical factors influencing release from matrix tablets .............. 25 1.14. Evaluation of controlled release matrix tablets .......................................... 28 1.15. In vitro Evaluation ..................................................................................... 28 1.16. In vivo performance evaluation ................................................................. 29 1.17. Data treatments ........................................................................................ 30 1.17.1 Zero-order treatment ................................................................................ 30
1.17.2 First-order treatment ................................................................................. 30
1.17.3 Higuchi’s model ......................................................................................... 30
1.17.4 Korsmeyer – Peppas model ...................................................................... 30
2. REVIEW OF LITERATURE .................................................................................. 33
2.1. Drug profile ................................................................................................... 42 2.1.1 Metformin HCl ........................................................................................... 42
2.1.2 Mechanism of action ................................................................................. 43
2.1.3 Dosage and administration ....................................................................... 44
VII
2.1.4 Adverse effects ......................................................................................... 44
2.1.5 Contraindications ...................................................................................... 45
2.1.6 Precautions ............................................................................................... 45
2.1.7 Identification test for Metformin HCl (I.P) .................................................. 45
2.1.8 Assay ........................................................................................................ 46
2.1.9 Packaging and storage ............................................................................. 46
2.2 Methocel ......................................................................................................... 47
2.2.1 Synonym: Hypromellose. .......................................................................... 47
2.2.2 Nomenclature ............................................................................................ 47
2.2.3 Preparation ............................................................................................... 48
2.2.4 Shelf life .................................................................................................... 48
2.2.5 Characteristics .......................................................................................... 48
2.2.6 Solubility .................................................................................................... 49
2.2.7 Properties .................................................................................................. 49
2.2.8 Substitution ............................................................................................... 49
2.3 Carboxy methyl cellulose ............................................................................... 50
2.3.1 Chemical family: Carbohydrate, Cellulose Derivative ............................... 50
2.3.2 Molecular structure ................................................................................... 50
2.3.3 Synonyms ................................................................................................. 50
2.3.4 Functional category ................................................................................... 50
2.3.5 Stability and storage ................................................................................. 51
2.3.6 Application ................................................................................................ 51
2.4 Cellulose acetate ............................................................................................ 52
2.4.1 Synonym ................................................................................................... 52
2.4.2 Introduction ............................................................................................... 52
2.4.3 Molecular structure ................................................................................... 52
2.4.4 Synthesis .................................................................................................. 52
2.4.5 Applications ............................................................................................... 53
2.4.6 Storage ..................................................................................................... 53
2.4.7 Stability ..................................................................................................... 53
2.5 Magnesium stearate ....................................................................................... 54
2.5.1 Synonym ................................................................................................... 54
2.5.2 Chemical name ......................................................................................... 54
VIII
2.5.3 Functional category ................................................................................... 54
2.5.4 Description ................................................................................................ 54
2.5.5 Application in formulation .......................................................................... 54
2.5.6 Stability and storage ................................................................................. 54
2.5.7 Incompatibilities ........................................................................................ 55
2.6 Aerosil ............................................................................................................. 56
2.6.1 Synonym ................................................................................................... 56
2.6.2 Chemical name ......................................................................................... 56
2.6.3 Storage ..................................................................................................... 56
2.6.4 Application ................................................................................................ 56
3. NEED FOR THE STUDY ....................................................................................... 58
4. OBJECTIVES AND HYPOTHESIS .................................................................. 61
6. METHODOLOGY ............................................................................................. 64
5.1 Preformulation studies..................................................................................... 64
5.1.1 Drug excipient compatibility studies .......................................................... 64
5.1.1.1 FTIR characterization ............................................................................ 65
5.1.1.2 Differential scanning calorimetry (DSC) ................................................. 65
5.1.1.3 Powder X-ray diffraction ........................................................................ 65
5.2 Pre-optimisation studies. ................................................................................. 66
5.2.1 Optimisation of polymer concentration. ........................................................ 66
5.3 Formulation development: .............................................................................. 66
5.3.1 Preparation of matrix tablets of Metformin HCl ......................................... 66
5.3.2 Preparation of 5% Cellulose acetate (CA) film: ......................................... 67
5.3.3 Preparation of swelling restricted matrix tablets: .......................................... 67
5.4 Evaluation of prepared tablets: ....................................................................... 69
5.4.1 Pre formulation studies................................................................................. 69
5.4.1.1 Bulk density ............................................................................................... 69
5.4.1.2 Hausner’s ratio .......................................................................................... 69
5.4.1.3 Carr’s compressibility index ....................................................................... 69
5.4.1.4 Angle of repose ......................................................................................... 70
5.4.2 Evaluation of physical properties of matrix tablets: ................................... 71
5.4.2.1 Thickness and diameter ............................................................................ 71
5.4.2.2 Weight variation test .................................................................................. 71
IX
5.4.2.3 Hardness test ............................................................................................ 71
5.4.2.4 Friability test .............................................................................................. 71
5.5 Swelling index of matrix tablets ....................................................................... 72
5.6 Drug content estimation .................................................................................. 73
5.7 In vitro release studies .................................................................................... 73
5.7.1 Preparation of standard curve for Metformin ............................................. 73
5.7.2 In vitro drug release studies ...................................................................... 74
5.8 RELEASE KINETIC MODELS ........................................................................ 75
5.8.1 Zero-order treatment .................................................................................... 75
5.8.2 First-order treatment .................................................................................... 76
5.8.3 Higuchi’s model ............................................................................................ 76
5.8.4 Korsmeyer – Peppas model ......................................................................... 77
5.9 SIMILARITY FACTOR..................................................................................... 78
5.10 STATISTICAL ANALYSIS 102 ........................................................................ 79
5.11 STABILITY STUDIES .................................................................................... 79
5.12 In vivo studies ............................................................................................... 80
5.12.1 Pharmacokinetics studies ......................................................................... 80
5.12.1.1 Blood Sample Collection ......................................................................... 80
5.12.1.2 Plasma samples extraction ..................................................................... 81
5.12.1.3 Method Validation of Metformin HCl in HPLC system ............................. 81
5.12.2 Pharmacodynamic studies ........................................................................ 83
5.12.2.1 Induction of Diabetes ............................................................................... 83
5.12.2.2 Experimental design ................................................................................ 83
5.12.2.3 Administration of drugs ............................................................................ 84
5.12.2.4 Blood Sample Collection and determination of blood glucose ................. 84
5.12.2.5 Body weight ............................................................................................. 84
6. RESULTS AND DISCUSSIONS ....................................................................... 86
6.1 Preformulation studies .................................................................................... 86
6.2 Compatibility studies ....................................................................................... 86
6.3 Pre-optimisation studies .................................................................................. 93
6.3.1 Optimisation of polymer concentration ......................................................... 93
6.4 Design and preparation of swelling restricted matrix tablet of ......................... 93
6.5 Evaluation of flow properties of powder .......................................................... 94
X
6.6 Evaluation of tablets ........................................................................................ 96
6.6.1 General appearance .................................................................................... 96
6.6.2 Hardness ...................................................................................................... 96
6.6.3 Thickness ..................................................................................................... 96
6.6.4 Weight variation test ..................................................................................... 97
6.6.5 Friability test ................................................................................................. 97
6.6.6 Drug content ................................................................................................. 97
6.7 Swelling index study ........................................................................................ 98
6.8 In vitro dissolution studies ............................................................................. 102
6.8.1 Preparation of calibration curve .................................................................. 102
6.9 In vitro drug release studies: ......................................................................... 103
6.12 Similarity factor: ........................................................................................... 112
6.13 In vivo release studies ................................................................................ 113
6.13.1 Pharmacokinetic study of Metformin HCl ................................................ 113
6.13.2 Pharmacodynamic study of Metformin HCl ............................................. 114
6.14 Statistical analysis ....................................................................................... 118
7. CONCLUSION ................................................................................................ 120
8. REFERENCES ............................................................................................... 124
9. ANNEXURE ........................................................................................................ 139
9.1 Annexure 1: List of Materials ......................................................................... 139
9.2 Annexure 2: List of Equipment ...................................................................... 140
9.3 Annexure 3: Published Journal Copy ............................................................ 141
9.4 Annexure 4: Animal ethical committee certificate ......................................... 144
XI
LIST OF FIGURES
Fig 1.1: Plasma drug concentration-time profile of conventional, zero order and
sustained release dosage forms. .................................................................. 2
Fig 1.2: Drug diffusion through matrix tablet ............................................................... 7
Fig 1.3: Diagram shows the three fronts of a swelling matrix tablets ........................ 18
Fig 1.4: Freely swellable matrix tablet ....................................................................... 19
Fig 1.5: Swelling restricted matrix tablet ................................................................... 19
Fig 6. 1 : FT-IR peak of different functional groups of Metformin HCl ....................... 87
Fig 6. 2 : FT-IR peak of different functional groups of Metformin HCl and HPMC K4M
.................................................................................................................................. 88
Fig 6. 3 : FT-IR peak of different functional groups of Metformin HCl and HPMC 15M
.................................................................................................................................. 89
Fig 6. 4 : FT-IR peak of different functional groups of Metformin HCl and HPMC K100M
.................................................................................................................................. 90
Fig 6. 5: DSC of pure Metformin HCl (a), Physical mixture of Metformin HCl with HPMC
K100M, Physical mixture of Metformin HCl with HPMC K100M and CMC. ............... 91
Fig 6. 6: X-ray diffraction studies of pure Metformin HCl and formulation blend
containing Metformin HCl, HPMC K100M and CMC. ................................................ 92
Fig 6. 7: Shows the swelling index of the formulations from MFH1 – MFH14 ........... 99
Fig 6. 8: Swelled tablet in SGF while conducting swelling index study. .................... 99
Fig 6. 9: Tablets formed gel like mass when conducting swelling index study ........ 100
Fig 6. 10: Calibration curve of Metformin HCl in distilled water ............................... 102
Fig 6. 11: Tablet removed at Q2 interval form dissolution study ............................. 103
Fig 6. 12: Performing dissolution test in type I apparatus ....................................... 104
Fig 6. 13 : In vitro dissolution profile of Metformin HCl matrix tablet. ...................... 107
XII
Fig 6. 14 : Dissolution profile of MFH 14 Vs SF14 (formulation after stability study)
................................................................................................................................ 111
Fig 6. 15:Dissolution profile of MFH 14 after long term stability study ..................... 112
Fig 6. 16: Comparative Plasma level of Metformin HCl in Rabbits .......................... 113
Fig 6. 17 : Effect of MFH 14 formulation on alloxan induced rabbits ....................... 115
Fig 6. 18: Effect of new formulation on body weight. .............................................. 116
Fig 6. 19: Chromatogram showing Metformin HCl and internal standard Glipizide . 117
XIII
LIST OF TABLES
Table 2.1: Parameters of Metformin HCl .................................................................. 43
Table 2.2: Physical and chemical properties of Avicel .............................................. 50
Table 2.3: Physical and chemical properties of Cellulose acetate ............................ 53
Table 2.4: Physical and chemical properties of Aerosil ............................................. 56
Table 5.1: Composition of matrix tablets containing Metformin HCl. ......................... 68
Table 5.2: Scale of flowability of powders ................................................................. 70
Table 5.3: Angle of repose and corresponding flow property .................................... 70
Table 5.4: Maximum allowable deviation for tablets ................................................. 71
Table 5.5: Value of ‘n’ with corresponding drug release mechanism ........................ 77
Table 5.6: Conditions as per ICH Guidelines. ........................................................... 80
Table 5.7: Treatment of different formulations to various groups of rabbit ................ 80
Table 5.8: Experimental Design for Pharmacodynamic studies in rabbit ................. 83
Table 6. 1: Result of visual inspection of Metformin HCl ........................................... 86
Table 6. 2: Solubility of Metformin HCl in different media ......................................... 86
Table 6. 3: Values of pre – compression parameters of developed formulations ...... 95
Table 6. 4: Observational report of various parameters of tablets ............................ 96
Table 6. 5: Results of post-compression parameters ................................................ 98
Table 6. 6: Showing results of % swelling index value of all formulations. .............. 101
Table 6. 7: Absorbance values of Metformin HCl in distilled water. ........................ 102
Table 6. 8: In Vitro %CDR of drug from Metformin HCl matrix tablets MFH1 to MFH 7
................................................................................................................................ 105
Table 6. 9: In vitro %CDR of drug from Metformin HCl matrix tablets MFH8 to MFH14
................................................................................................................................ 106
XIV
Table 6. 10: Correlation coefficient values and release kinetics of Metformin HCl
matrix tablets ........................................................................................................... 109
Table 6. 11: Results of short term stability study of MFH14 .................................... 110
Table 6. 12: Results of Long term stability study of MFH14 .................................... 112
Table 6. 13: Pharmacokinetic parameters obtained from three different formulations
of Metformin HCl in rabbits (using Residual method PK analysis) ........................... 117
XV
LIST OF ABBREVATIONS AND SYMBOLS
AVG Average
AUC Area under curve
MEC Minimum effective concentration
GI Gastro intestine
Cl Clearance
GIT Gastro intestinal tract
h Hour
CR Controlled release
ER Extended release
CRDDS Controlled release drug delivery system
CA Cellulose acetate
SR Sustained Release
SF Standard formulation
HPMC Hydroxypropyl methyl cellulose
CMC Carboxy methyl cellulose
USP United States Pharmacopoeia
IP Indian Pharmacopoeia
ICH International Conference on Harmonisation
PEG Poly ethylene Glycol
FTIR Fourier transform infrared spectroscopy
SLS Sodium lauryl sulphate
SGF Simulated Gastric Fluid
SIF Simulated Intestinal Fluid
DSC Differential scanning calorimetry
LDL Low density lipoprotein
IR Infra-Red
HPLC High performance liquid chromatography
XVI
CDR Cumulative drug release
PK Pharmacokinetic
cc Cubic centimetre
i.p Intra peritoneal
p.o Per-oral
rpm Rotations per minute
Mg Magnesium
mPa.s Millipascal - seconds
i.e. That is
e.g. Example
Tg Glass transition temperature
mg Milligram
ng Nano gram
ºC Degree Celsius
ºF Degree Fahrenheit
ml Millilitre
cm centimetre
mm millimetre
nm nanometre
kg Kilogram
% Percentage
s Seconds
min Minutes
W Weight
w/v weight by volume
SD Standard Deviation
RH Relative Humidity
Fig Figure
q.s Quantity sufficient
XVII
Q2 Drug release at 2 h
Q8 Drug release at 8 h
Q12 Drug release at 12 h
g/mol Gram per mol
mmol/L millimol per litre
mg/dl milligram per decilitre
g Gram
cPs Centipoise
µm Micro meter
Å Angstrom
λ Lambda
I INTRODUCTIONCHAPTER 1
1
1. INTRODUCTION
Oral route has been one of the most popular commonly employed routes
of drug delivery due to its ease of administration, patient compliance, least
sterility constraints, flexible design of dosage forms and cost effectiveness to
manufacturing process1. Tablets are most popular oral formulations available in
market and preferred by patients and physicians alike. This type of drug delivery
system is called conventional drug delivery system and is known to provide an
immediate release of drug. Such immediate release products results in relatively
rapid drug absorption and onset of accompanying pharmacodynamic effects.
However, after absorption of drug from the dosage form is complete, plasma
drug concentrations decline according to the drug’s pharmacokinetics profile.
Eventually, plasma drug concentrations fall below the minimum effective plasma
concentration (MEC), resulting in loss of therapeutic activity2. Before this point
is reached another dose is usually given if a sustained therapeutic effect is
desired. These dosage forms have been found to have the following serious
limitations.
Inconvenient due to periodic administration
Difficult to monitor
Non-specific administration
Careful calculation necessary to prevent overdosing
Drug goes to non-target cells and can cause damage
Low concentrations can be ineffective
2
1.1. Oral controlled drug delivery system
An alternative to administration of another dose is to use a dosage form
that will provide sustained drug release, and therefore, maintain plasma drug
concentrations. Oral extended release drug delivery system becomes a very
promising approach for those drugs that are given orally but having the shorter
half-life and high dosing frequency. Controlled release formulations are much
desirable and preferred for such therapy because they offer better patient
compliance, maintain uniform drug levels, reduced dose and side effects and
increased margin of safety for high potency drugs3.
Plasma drug concentration profiles for conventional tablet formulation, a
sustained release formulation, and a zero order controlled release formulation
is shown in Fig 1. 1.
Fig 1. 1 : Plasma drug concentration-time profile of conventional, zero order and sustained release dosage forms4.
3
An ideal dosage form for the treatment of any disease is the one which
immediately attain a therapeutic plasma level and maintain it constant for the
entire period of treatment. This is possible through administration of
conventional dosage form at a particular frequency. But with conventional
dosage form there is unavoidable fluctuation in the drug plasma level which can
be overcome by use of sustain release dosage form5. Sustain release is a term
use to characterize a delivery system which is designed in such a manner to
achieve a prolonged therapeutic effect by continuously releasing the drug over
an extended period of time after administration of a single dose. The term
“controlled release” has been associated with those systems which release their
active principle at a predetermined rate6. Physician can achieve certain
desirable therapeutic benefit by prescribing controlled release dosage forms;
since the frequency of drug administered is reduced the patient compliance gets
improved. The blood level oscillation characteristic of multiple dosing of
conventional dosage form is also reduced, as a more even blood level is
maintained.
Advantages7:
1. Maintains therapeutic concentrations over prolonged periods.
2. Avoids the high blood concentration.
3. Reduction in toxicity by slowing drug absorption.
4. Minimize the local and systemic side effects.
5. Improvement in treatment efficacy.
6. Better drug utilization
4
7. Minimize drug accumulation with chronic dosing.
8. Can be made to release high molecular weight compounds.
9. Improved patient compliance.
10. Economical (Although the initial cost of treatment is high the overall
treatment cost will be less due to less dosing frequency).
Disadvantages7:
1. The remaining matrix must be removed after the drug has been released.
2. Greater dependence on GI residence time of dosage form.
3. Increased potential for first-pass metabolism.
4. Delay in onset of drug action.
5. Release rates are affected by food and the rate transit through the gut.
6. Release rate continuously diminishes due to increased diffusional
resistance and decrease in effective area at the diffusion front.
1.2. Challenges in controlled release formulations:
1. Cost of formulation i.e. preparation and processing.
2. Fate of controlled release system if not biodegradable.
3. Biocompatibility.
4. Fate of polymer additives, e.g., plasticizers, stabilizers, antioxidants.
5. Dose dumping (Chewing or grinding of oral formulation by the patients).
7. Retrieval of drug is difficult in case of toxicity, poisoning or hypersensitivity
reaction.
5
1.3. Rationale for designing controlled drug delivery7:
Reducing the frequency and quantity of dose.
To increase effectiveness of the drug by localization at the site of action.
To avoid an undesirable local action within the GIT.
To provide programmed and uniform drug delivery pattern.
To increase extend of absorption/bioavailability.
To extend the time of action of drug after administration.
The basic rationale of a controlled drug delivery system is to optimize the
biopharmaceutic, pharmacokinetic and pharmacodynamic properties of a drug
in such a way that its utility is maximized through reduction in side effects and
cure or control of condition in the shortest possible time by using smallest
quantity of drug administered by the most suitable route.
Ideal drug candidates for controlled drug delivery systems must meet the
following criteria’s:
1. It should be orally effective and stable in GIT medium.
2. Drugs with short half-lives, ideally a drug with half-life in the range of 2 –
4 H makes a good candidate for formulation into CR dosage forms.
3. The dose of the drug should be less than 0.5 g as the oral route is suitable
for drugs given in dose as high as 1.0 g.eg. Metronidazole.
4. A drug for CRDDS should have therapeutic range wide enough such that
variations in the release do not result in concentration beyond the
minimum toxic levels.
6
Potential areas to be considered are:
The various pH that the dosage form would encounter during its transit
The gastrointestinal motility
The enzyme system and its influence on the drug and the dosage form
1.4. Matrix tablets:
Historically, the most popular drug delivery system till date is the matrix
because of its low cost and ease of fabrication. Introduction of matrix tablet as
sustained release has given a new break through from the novel drug delivery
system in the field of pharmaceutical technology. The drug release from the
dosage form is controlled mainly by the type and proportion of polymer used in
the preparation.
Matrix tablet may be defined as “oral solid dosage form in which the drug
or active ingredient is homogeneously dispersed throughout the hydrophobic or
hydrophilic matrices which serves as release rate retardants”7.
These systems release drug in continuous manner by dissolution
controlled or diffusion controlled mechanisms (as shown in Fig 1. 2). Usually the
drug release from these matrices includes penetration of fluid, followed by
dissolution of drug particles and diffusion through fluid filled pores. The diffusion
of drug through a matrix is a rate limiting step.
Matrix tablets serves as an important tool for oral extended- release dosage
forms. They can be formulated by wet granulation or direct compression
methods by dispersing solid particles within a porous matrix formed of
7
hydrophilic and hydrophobic polymers. The use of different classes of polymers
in controlling the release of drugs has become the most important aspect in the
formulation of matrix tablets.
Fig 1. 2: Drug diffusion through matrix tablet 8
1.5. Polymers used in matrix tablets9:
There are number of polymers which may be used to formulate matrix
tablets depending on the physicochemical properties of the drug substance to
be incorporated into matrix system and type of drug release required. Polymers
used for matrix tablets may be classified as:
1. Hydrogels
a. Polyhydroxy ethyl methyl acrylate (PHEMA)
b. Cross linked polyvinyl alcohol (PVA)
c. Cross linked polyvinyl pyrrolidone (PVP)
d. Polyethylene oxide (PEO)
e. Polyacrylamide (PA)
8
2. Soluble polymers
a. Polyethylene glycol (PEG)
b. Polyvinyl alcohol (PVA)
c. Polyvinyl pyrrolidone (PVP)
d. Hydroxypropyl methyl cellulose (HPMC)
3. Biodegradable polymers
a. Polylactic acid (PLA)
b. Polyglycolic acid (PGA)
c. Polycaprolactone (PCL)
d. Polyanhydrides
e. Polyorthoesters
4. Non-biodegradable polymers
a. Polydimethyl siloxane (PDS)
b. Polyethylene vinyl acetate (PVA)
c. Polyether urethane (PEU)
d. Polyvinyl chloride (PVC)
e. Cellulose acetate (CA)
5. Mucoadhesive polymers
a. Polycarbophil
b. Sodiumcarboxy methyl cellulose
c. Polyacrylic acid
d. Tragacanth
e. Methyl cellulose
9
6. Natural gums
a. Xanthan gum
b. Guar gum
c. Karaya gum
d. Gum Arabic
e. Locust bean gum
Various synthetic and natural polymers have been examined in drug
delivery applications. The three key advantages that polymeric drug delivery
products can offer are:
Localized delivery of drug
Sustained delivery of drug
Stabilization of drug (protects the drug from GIT environment)
1.6. Classification of matrix tablets9, 10:
1. On the basis of type of polymer/release rate retardant used matrix tablets
may be divided into two types.
a) Hydrophilic matrix tablet
b) Hydrophobic matrix tablet
2. On the basis of porosity of the matrix system used in the formulation.
a) Macro porous system.
b) Micro porous system.
c) Non porous system.
10
1.6.1. Hydrophilic matrix tablet11
Hydrophilic matrix tablets may be defined as “Homogeneous dispersion
of drug molecules within a skeleton of hydrophilic polymers, such as cellulose
derivatives, sodium alginate, xanthan gum, polyethylene oxide, or carbopol
among others, that swells upon contact with water”.
These systems are called swellable-controlled release systems. Apart
from swelling and diffusion mechanisms polymer dissolution is another
important mechanism that can modulate the drug delivery rate. Swelling or
dissolution can be the predominant factors for a specific type of polymers, in
most cases drug release kinetics is a result of a combination of these two
mechanisms13. The release rate observed is possibly the zero-order release.
The polymers used in the preparation of hydrophilic matrices are divided in to
two broad groups 14.
A. Cellulose derivatives: Methylcellulose 400 and 4000 cPs, hydroxyl ethyl
cellulose, hydroxypropyl methylcellulose (HPMC) 25, 100, 4000 and
15000cPs and sodium carboxy methylcellulose.
B. Non cellulose natural or semi synthetic polymers: Agar-Agar, carbo gum,
alginates, molasses, polysaccharides of mannose and galactose,
chitosan and modified starches.
11
1.6.2. Hydrophobic matrix tablets
This system was first introduced in 1959. In this method, drug is mixed
with an inert or hydrophobic polymer and then compressed into a tablet.
Sustained release is produced due to the fact that the dissolving drug has
diffused through a network of channels that exist between compacted polymer
particles. This is the only system where the use of polymer is not essential to
provide controlled drug release, although insoluble polymers have been used.
The primary rate-controlling components of hydrophobic matrix are water
insoluble in nature. Examples of materials that have been used as inert or
hydrophobic matrices include waxes, glycerides, polyethylene, polyvinyl
chloride, ethyl cellulose and acrylate polymers and their copolymers 15, 16.
The rate-controlling step in these formulations is liquid penetration into
the matrix. The possible mechanism of release of drug in such type of tablets is
diffusion. Such types of matrix tablets become inert in the presence of water and
gastrointestinal fluid. The presence of insoluble ingredient in the formulations
helps to maintain the physical dimension of hydrophobic matrix during drug
release. To modulate drug release, it may be necessary to incorporate soluble
ingredients such as lactose into formulation13.
Macro porous Systems: In such systems the diffusion of drug occurs through
pores of matrix, which are of size range 0.1 to 1 μm. This pore size is larger than
diffusant molecule size.
12
Micro porous System: Diffusion in this type of system occurs essentially
through pores. For micro porous systems, pore size ranges between 50 – 200
Å, which is slightly larger than diffusant molecules size.
Non-porous System: Non-porous systems have no pores and the molecules
diffuse through the network meshes. In this case, only the polymeric phase
exists and no pore phase is present.
1.7. Mechanism of drug release from matrix tablet12:
Drug in the outside layer exposed to the bathing solution is dissolved first
and then diffuses out of the matrix. This process continues with the interface
between the bathing solution and the solid drug moving toward the interior. It
follows that for this system to be diffusion controlled, the rate of dissolution of
drug particles within the matrix must be much faster than the diffusion rate of
dissolved drug leaving the matrix.
Derivation of the mathematical model to describe this system involves the
following assumptions:
1. A pseudo-steady state is maintained during drug release.
2. The diameter of the drug particles is less than the average distance of
drug diffusion through the matrix.
3. The bathing solution provides sink conditions at all times.
13
The release behaviour for the system can be mathematically described by the
following equation:
dM/dh = C0. dh – Cs/2 ……………… (I)
Where,
dM = Change in the amount of drug released per unit area.
dh = Change in the thickness of the zone of matrix that has been depleted
of drug.
C0 = Total amount of drug in a unit volume of matrix.
Cs = Saturated concentration of the drug within the matrix.
Additionally, according to diffusion theory:
dM = ( Dm. Cs / h) dt........................... (II)
Where,
Dm = Diffusion coefficient in the matrix.
h = Thickness of the drug-depleted matrix.
dt = Change in time.
By combining equation (i) and equation (ii) and integrating:
M = [Cs. Dm (2C0 –Cs) t] 1/2 ………… (III)
When the amount of drug is in excess of the saturation concentration then:
M = [2Cs.Dm.C0.t] 1/2 ……………….… (IV)
Equation (III) and eq. (IV) relate the amount of drug release to the square-
root of time. Therefore, if a system is predominantly diffusion controlled, then it
is expected that a plot of the drug release Vs square root of time will result in a
straight line. Drug release from a porous monolithic matrix involves the
simultaneous penetration of surrounding liquid, dissolution of drug and leaching
14
out of the drug through tortuous interstitial channels and pores. The volume and
length of the openings must be accounted for in the drug release from a porous
or granular matrix:
M = [Ds.Ca.p/T. (2Co – p.Ca) t] 1/2 …………… (V)
Where,
p = Porosity of the matrix
t = Tortuosity
Ca = solubility of the drug in the release medium
Ds = Diffusion coefficient in the release medium.
T = Diffusional path length
For pseudo steady state, the equation can be written as:
M = [2D.Ca .C0 (p/T) t] 1/2 …………………... (VI)
The total porosity of the matrix can be calculated with the following equation:
p = pa + Ca/ ρ +Cex/ρex…………………….… (VII)
Where,
p = Porosity
ρ = Drug density
pa = Porosity due to air pockets in the matrix
ρex = Density of the water soluble excipients
Cex = Concentration of water soluble excipients
For the purpose of data treatment, equation (VII) can be reduced to:
M = k. t 1/2 …………………………… (VII)
Where, k = constant.
15
So the amount of drug released versus the square root of time will be
linear, if the release of drug from matrix is diffusion-controlled. If this is the case,
the release of drug from a homogeneous matrix system can be controlled by
varying the following parameters:
1. Initial concentration of drug in the matrix
2. Porosity
3. Tortuosity
4. Polymer system forming the matrix
5. Solubility of the drug
1.8. Bimodal Release17, 18:
In some systems there is anomalous release of the active ingredient. In
these systems release is primarily by diffusion. Sometimes the ER polymer may
become hydrated and begin to dissolve leading to release upon erosion. These
systems are complex and difficult to mathematically model since the diffusional
path length undergoes change due to the polymer dissolution. A series of
transport phenomena are involved in the release of a drug from a swellable,
diffusion/erodible matrix:
1. Initially, there are steep water concentration gradients at the
polymer/water interface, resulting in absorption of water into the matrix.
2. Due to the absorption of water, the polymer swells, resulting in dramatic
changes of drug and polymer concentration, increasing the dimensions of
the system and increasing macromolecular mobility.
16
3. Upon contact with water the drug dissolves and diffuses out of the device.
4. With increasing water content, the diffusion coefficient of the drug
increase substantially.
5. In the case of a poorly water-soluble drug, dissolved and undissolved drug
coexist within the polymer matrix.
6. Finally, the polymer itself dissolves.
Swellable matrix tablets are activated by water, and drug release control
depends on the interaction between water, polymer and drug. Water penetration
is the first step leading to polymer swelling and polymer and drug dissolution.
The presence of water decreases the glassy rubbery temperature (e.g., for
HPMC from 184°C to lower than 37°C), giving rise to the transformation of
glassy polymer in a rubbery phase (gel layer). The enhanced mobility of the
polymeric chain favours the transport of dissolved drug. Polymer relaxation
phenomena determine the swelling or volume increase of the matrix. The latter
may add a convective contribution to the drug transport mechanism in drug
delivery.
The gel layer thickness depends on the relative contributions of water
penetration, chain disentanglement, and mass (polymer and drug) transfer in
water. At the beginning the water penetration is more rapid than chain
disentanglement and a quick build-up of gel layer thickness takes place. But
when the water penetrates slowly, due to the increase of the diffusional distance,
little chance in the gel thickness is obtained because water penetration and
17
polymer disentanglement rates are similar. Thus the gel layer thickness
dynamics in swellable matrix tablet shows three distinct phases:
1. It increases when the penetration of water is the fastest phenomenon.
2. Stays constant when the disentanglement rate is similar to the
penetration.
3. Decreases when the entire polymer is in the rubbery phase.
1.9. Boundaries of gel layer and relevant fronts19:
It is common knowledge that the gel layer thickness is defined by the front
separating the matrix from the dissolution medium. The penetration of the
medium into the matrix is accompanied by the formation of a series of fronts (Fig
1. 3) which later disappear along the process of matrix dissolution. The following
fronts have been defined with regard to anomalous release systems:
1. The swelling front: The boundary between the still glassy polymer and its
rubbery phase. With the entry of water into the matrix, the polymer passes
from the crystalline state to a hydrated or jellified state.
The rubbery zone is characterized by being the one into which more
solvent has entered and hence the vitreous transition temperature
(Tg) at 37°C of the polymer is lower than the experimental
temperature.
The glassy region is the one into which the least solvent has
entered and hence its Tg is higher than the experimental
temperature.
18
2. Diffusion front (solid drug–drug solution boundary): The boundary
between the solid as yet undissolved drug and the dissolved drug in gel
layer.
3. The erosion front or dissolution front: The boundary between the matrix
and dissolution medium.
By using sufficient soluble polymers, the gel layer thickness remains
constant, since the fronts in the matrix move in a synchronised way. Keeping
constant the releasing area, this situation leads to zero-order release.
Erosion Front Diffusion Front Swelling Front
Fig 1. 3 : Diagram shows the three fronts of a swelling matrix tablets
1.10. Swellable matrix tablets as drug delivery systems19, 94:
Swelling controlled release systems for drug delivery are very often
prepared as monoliths, i.e., matrices formed by compression of hydrophilic
micro particulate powders. The amount of swellable polymers usually range
from 10-30% of the total weight of the matrix. Different types of swellable matrix
tablets can be prepared by the use of hydrophilic polymers, such as:
19
1. Free swellable matrix tablets: Polymers and solid drug mixed and
compressed, in which swelling is unhindered (as shown in Fig 1. 4).
Fig 1. 4 : Freely swellable matrix tablet
2. Swelling restricted matrix tablets: Their function is to alter the swelling
behaviour and then the drug release. The partial coating of swellable
matrix tablets containing soluble polymers with impermeable films
(Cellulose acetate) created conditions for attainment of zero-order
release (as shown in Fig 1. 5).
A B C
Fig 1. 5 : Swelling restricted matrix tablet (Blue colour illustrates coating with Polymer)
3. Swelling controlled reservoir system: Swellable polymers are used as
coating for delaying or controlling the diffusion of drug from the core.
1.11. Factors affecting drug release from a matrix system20:
1. Drug solubility: Molecular size and water solubility of drug are important
determinants in the release of drug from swelling and erosion controlled
A B C
20
polymeric matrices. For drugs with reasonable aqueous solubility, release
of drugs occurs by dissolution in infiltrating medium and for drugs with
poor solubility release occurs by both dissolution of drug and dissolution
of drug particles through erosion of the matrix tablet.
2. Polymer diffusivity: The diffusion of small molecules in polymer structure
is energy activated process in which the diffusant molecules moves to a
successive series of equilibrium position when a sufficient amount of
energy of activation for diffusion, Ed has been acquired by the diffusant is
dependent on length of polymer chain segment, cross linking and
crystallinity of polymer. The release of drug may be attributed to the three
factors:
a. Polymer particle size: e.g. when the content of hydroxyl propyl
methylcellulose (HPMC) is higher, the effect of particle size is less
important on the release rate of propranolol hydrochloride, the
effect of this variable is more important when the content of polymer
is low. Results may be justified by considering that in certain areas
of matrix containing low levels of HPMC led to the burst release.
b. Polymer viscosity: With cellulose ether polymers, viscosity is used
as an indication of matrix weight. Increasing the molecular weight
or viscosity of the polymer in the matrix formulation increases the
gel layer viscosity and thus slows drug dissolution. Also, the greater
viscosity of the gel, the more resistant the gel is to dilution and
erosion, thus controlling the drug dissolution.
21
c. Polymer concentration: An increase in polymer concentration
causes an increase in the viscosity of gel as well as formulation of
gel layer with a longer diffusional path. This could cause a decrease
in the effective diffusion coefficient of the drug and therefore
reduction in drug release. The mechanism of drug release from
matrix also changes from erosion to diffusion as the polymer
concentration increases.
3. Thickness of polymer diffusional path: The controlled release of a drug
from both capsule and matrix type polymeric drug delivery system is
essentially governed by Fick’s law of diffusion:
JD = D dc/dx
Where,
JD = Flux of diffusion across a plane surface of unit area.
D = diffusibility of drug molecule.
dc/dx = is conc. gradient of drug molecule across a diffusion path
with thickness dx.
4. Thickness of hydrodynamic diffusion layer: It was observed that the drug
release profile is a function of the variation in thickness of hydrodynamic
diffusion layer on the surface of matrix type delivery devices. The
magnitude of drug release value decreases on increasing the thickness
of hydrodynamic diffusion layer.
5. Drug loading dose: The loading dose of drug has a significant effect on
resulting release kinetics along with drug solubility. The effect of initial
drug loading of the tablets on the resulting release kinetics is more
22
complex in case of poorly water soluble drugs, with increasing initial drug
loading the relative release rate first decreases and then increases,
whereas, absolute release rate increases. In case of freely water soluble
drugs, the porosity of matrix upon drug depletion increases with
increasing initial drug loading. This effect leads to increased absolute drug
transfer rate. But in case of poorly water soluble drugs, another
phenomenon also has to be taken in to account. When the amount of drug
present at certain position within the matrix, exceeds the amount of drug
soluble under given conditions, the excess of drug has to be considered
as non-dissolved and thus not available for diffusion. The solid drug
remains within tablet, on increasing the initial drug loading of poorly water
soluble drugs, the excess of drug remaining with in matrix increases.
6. Surface area and volume: The dependence of the rate of drug release on
the surface area of drug delivery device is well known theoretically and
experimentally. Both the in-vitro and in-vivo rate of the drug release, are
observed to be dependent upon surface area of dosage form. Siepman
et al. found that release from small tablet is faster than large cylindrical
tablets.
7. Diluent’s effect: The effect of diluent or filler depends upon the nature of
diluent. Water soluble diluents like lactose, mannose cause marked
increase in drug release rate and release mechanism is also shifted
towards Fickian diffusion; while insoluble diluents like dicalcium
phosphate reduce the Fickian diffusion and increase the relaxation
23
(erosion) rate of matrix. The reason behind this is that water soluble filler
in matrices stimulate the water penetration in to inner part of matrix, due
to increase in hydrophilicity of the system, causing rapid diffusion of drug,
leads to increased drug release rate.
1.12. Biological factors influencing release from matrix tablets95:
1. Biological half-life: SR product aims to maintain therapeutic blood levels
over an extended period of time. In order to achieve this, drug must enter
the circulation at approximately the same rate at which it is eliminated.
The elimination rate is quantitatively described by the half-life (t1/2). Each
drug has its own characteristic elimination rate, which is the sum of all
elimination processes, including metabolism, urinary excretion and all
over processes that permanently remove drug from the blood stream.
Therapeutic compounds with short half-life are generally are excellent
candidate for SR formulation, as this can reduce dosing frequency. In
general, drugs with half-life shorter than 2 h such as furosemide or
levodopa are poor candidates for SR preparation. Compounds with long
half-lives, more than 8 h are also generally not used in sustaining form,
since their effect is already sustained. E.g. Digoxin and phenytoin.
2. Absorption: Since the purpose of forming a SR product is to place control
on the delivery system, it is necessary that the rate of release is much
slower than the rate of absorption. If we assume that the transit time of
most drugs in the absorptive areas of the GI tract is about 8-12 h, the
24
maximum half-life for absorption should be approximately 3-4 h;
otherwise, the device will pass out of the potential absorptive regions
before drug release is complete. Thus corresponds to a minimum
apparent absorption rate constant of 0.17-0.23 to give 80-95% over this
time period. Hence, it assumes that the absorption of the drug should
occur at a relatively uniform rate over the entire length of small intestine.
If a drug is absorbed by active transport or transport is limited to a specific
region of intestine, SR preparation may be disadvantageous to
absorption. One method to provide sustaining mechanisms of delivery for
compounds tries to maintain them within the stomach. This allows slow
release of the drug, which then travels to the absorptive site. These
methods have been developed as a consequence of the observation that
co-administration results in sustaining effect.
3. Metabolism: Drugs those are significantly metabolized before absorption,
either in the lumen or the tissue of the intestine, can show decreased
bioavailability from slower-releasing dosage form. Hence, criteria for the
drug to be used for formulating SR dosage form is:
Drug should have short half-life (2-4 h.)
Drug should be soluble in water
Drug should have large therapeutic window
Drug should be absorbed throughout the GIT
25
Even a drug that is poorly water soluble can be formulated in SR dosage
form. For the same, the solubility of the drug should be increased by the
suitable system and later on that is formulated in the SR dosage form.
4. Distribution: Drugs with high apparent volume of distribution, which
influence the rate of elimination of the drug, are poor candidate for oral
SR drug delivery system e.g. Chloroquine.
5. Protein Binding: The Pharmacological response of drug depends on
unbound drug concentration drug rather than total concentration and all
drug bound to some extent to plasma and or tissue proteins. Proteins
binding of drug play a significant role in its therapeutic effect regardless
the type of dosage form as extensive binding to plasma increase
biological half-life and thus sometimes SR drug delivery system is not
required for this type of drug.
6. Margin of safety: As we know larger the value of therapeutic index safer
is the drug. Drugs with low therapeutic index are usually poor candidate
for formulation of oral SR drug delivery system due to technological
limitation of control over release rates.
1.13. Physicochemical factors influencing release from matrix
tablets21, 94:
1. Dose size: For orally administered systems, there is an upper limit to the
bulk size of the dose to be administered. In general, a single dose of 0.5-
26
1.0 g is considered maximal for a conventional dosage form. This also
holds true for sustained release dosage form. Compounds that require
large dosing size can sometimes be given in multiple amounts or
formulated into liquid systems. Another consideration is the margin of
safety involved in administration of large amount of a drug with a narrow
therapeutic range.
2. Ionization, pka and aqueous solubility: Most drugs are weak acids or
bases. Since the unchanged form of a drug preferentially permeates
across lipid membranes, it is important to note the relationship between
the pka of the compound and the absorptive environment. Presenting the
drug in an unchanged form is advantageous for drug permeation. Delivery
systems that are dependent on diffusion or dissolution will likewise be
dependent on the solubility of the drug in aqueous media. These dosage
forms must function in an environment of changing pH, the stomach being
acidic and the small intestine more neutral, the effect of pH and release
process must be defined. Compounds with very low solubility
(<0.01mg/ml) are inherently sustained, since their release over the time
course of a dosage form in the GI tract will be limited by dissolution of the
drug. So it is obvious that the solubility of the compound will be poor
choices for slightly soluble drugs, since the driving force for diffusion,
which is the drug’s concentration in solution, will be low.
3. Partition Coefficient: When a drug is administered to the GI tract, it must
cross a variety of biological membranes to produce a therapeutic effect in
27
another area of the body. It is common to consider that these membranes
are having lipophilic nature; therefore the partition coefficient of oil-soluble
drugs becomes important in determining the effectiveness of membrane
barrier penetration. Compounds which are lipophilic in nature having high
partition coefficient are poorly aqueous soluble and it retain in the
lipophilic tissue for the longer time. In case of compounds with very low
partition coefficient, it is very difficult for them to penetrate the membrane,
resulting in poor bioavailability. Furthermore, partitioning effects apply
equally to diffusion through polymer membranes. The choice of diffusion-
limiting membranes must largely depend on the partitioning
characteristics of the drug.
4. Stability: Orally administered drugs can be subject to both acid-base
hydrolysis and enzymatic degradation. Degradation will proceed at a
reduced rate for drugs in solid state; therefore, this is the preferred
composition of delivery for problem cases. For the dosage form that are
unstable in stomach, systems that prolong delivery over entire course of
transit in the GI tract are beneficial; this is also true for systems that delay
release until the dosage form reaches the small intestine. Compounds
that are unstable in small intestine may demonstrate decreased
bioavailability when administered from a sustaining dosage form. This is
because more drugs is delivered in the small intestine and, hence, is
subject to degradation. Propentheline and probanthine are representative
example of such drug.
28
1.14. Evaluation of controlled release matrix tablets:
Before marketing a controlled release product it is necessary to assure
the strength, safety, stability and reliability of the product by performing in vitro
and in vivo analysis and correlation between the two.
1.15. In vitro Evaluation:
For solid oral controlled release dosage forms, drug release
characterisation is the most important among various in vitro tests because the
in vivo absorption is determined by the release kinetics of the dosage forms. A
validated in vitro dissolution test can serve the purposes of
1. Providing necessary quality and process control
2. Determining stability of the relevant release characteristics of the product
3. Facilitating certain regulatory determinations and judgments concerning
minor formulation changes, change in site of manufacture
However the dissolution rate of a specific dosage is essentially arbitrary
parameter that may vary with the dissolution methodology, such as type of
apparatus, medium, agitation, etc. The key elements during the dissolution
evaluation include:
a) Reproducibility of the method
b) Maintenance of sink condition
c) Dissolution profile with a narrow limit on 1-h specification to assure lack
of dose dumping
29
d) At least 75% of drug released at the last sampling interval to assure
complete release
Commonly used USP dissolution methods are recommended for determination
of drug release from oral controlled release dosage forms are96;
I. USP apparatus I (basket method): Preferred for capsules and dosage
forms that tend to float or disintegrate slowly.
II. USP apparatus II (Paddle method): Preferred for tablets.
III. USP apparatus III (Bio-Dis dissolution method, or modified
disintegration): Useful for bead type dosage form.
IV. USP apparatus IV (Flow-through cell method): For insoluble drugs.
1.16. In vivo performance evaluation:
Once the satisfactory In vitro profile is achieved, it becomes necessary to
conduct in vivo evaluation and establish an in vitro - in vivo correlation. The
various in vivo evaluation methods are:-
a) Clinical response
b) Blood level data
c) Urinary excretion studies
d) Nutritional studies
e) Toxicity studies
f) Radioactive tracer techniques
30
1.17. Data treatments
1.17.1 Zero-order treatment 22
Qt = Q0+K0t
Where, Qt = Amount of drug released in time (t).
Q0 = Initial amount of drug in solution,
K0 = Zero order release constant.
1.17.2 First-order treatment 23, 24
Log c = Log c0 – kt / 2.303
Where, c = amount of drug remaining unreleased at time t.
C0 = initial amount of drug in solution.
K = first order rate constant.
1.17.3 Higuchi’s model 24, 25
Qt = kt1/2
Where, Qt = amount of drug released in time t
K = Higuchi’s constant.
A linear relationship between amount of drug released (Q) versus square root
of time (t1/2) is observed if the drug release from the matrix is diffusion controlled.
1.17.4 Korsmeyer – Peppas model 27
It relates that the drug release is exponentially to time. It is described by the
following equation;
Mt / Minf = atn
31
Where, Mt / Minf = fraction release of drug.
a = constant depending on the structural and geometric
characteristics of the drug dosage form.
n = release exponent.
The value of n indicates the drug release mechanism.
For slab:
n = 0.5 (indicates Fickian diffusion)
n = 0.5 – 1.0 or n = 1 (indicates non – Fickian mechanism)
For cylinder:
n = 0.45 instead of 0.5 and 0.89 instead of 1.0.
This model is used to analyse the release of drug from polymeric dosage form,
when the release mechanism is not understood or when there is a possibility of
more than one type of release mechanisms are involved.
32
REVIEW OF LITERATURECHAPTER 2
33
2. REVIEW OF LITERATURE
Sandhya28 et. al in 2014 prepared bilayered tablet containing Glimepiride
(immediate release) and Metformin HCl (Sustained release). Tablets were
prepared using different polymers (HPMC, Povidone, Ethyl cellulose) which
were evaluated and in vitro release profiles were recorded. It had sufficient
floating properties and developed formulations gave near to zero order release
pattern which followed higuchi model.
Damodar29 et. al in 2014 developed immediate and sustained release
Metformin HCl tablet. Immediate release was prepared by direct compression
and sustained release beads were prepared by inotropic gelation method and
its evaluation were done. All tablets contained micro beads up to 35% and were
within specified limits.
Babu30 et. al in 2014 prepared Metformin HCl sustained release tablets using
wet granulation technique with polymers such as Xanthan gum, Guar gum,
HPMC and Eudragit. Different batches were prepared using varying
concentration of polymers and its evaluation were done. From the dissolution
studies it was found that guar gum used tablets gave a drug release of 12 h and
showed slower release rate when compared to others. Most of the formulations
followed zero order release pattern.
Hasan31 et. al in 2014 developed extended release Metformin HCl tablet by
direct compression using varying drug-polymer ratio. Drug release were
retarded with Methocel K100MCR premium and Xanthan Gum. Precompression
and post compression parameters were evaluated and were within acceptable
34
limits. F3, F4 and F5 gave better release than others. Data were fitted into
various kinetic models and found that that diffusion along with erosion could be
the mechanism of drug release.
Solanki32 et. al in 2014 formulated Metformin HCl sustained release tablets by
wet granulation technique. Prepared tablets exhibited sustained release profile
for an extended period of time. It showed non-fickian diffusion release
mechanism and compatibility studies showed that there was no interaction
between the excipients.
Reddy33 et. al in 2013 formulated sustained release tablets of Metformin HCl by
wet granulation using different ratio of polymers (Xanthan Gum, Guar Gum).
Prepared tablets using natural polymers gave better sustained release profile
than synthetic polymers. Prepared tablets had 87.02% release at 8h whereas
marketed once had 105.6% drug release at 8h.
Saluja34 in 2013 designed once daily sustained release matrix tablet containing
Metformin HCl using Chitosan and HPMC phthalate by wet granulation method.
From 8 formulations A-H granulating agent for A was PVP in isopropyl alcohol
and formulation B-H by decreasing concentration of Chitosan and HPMCP.
Formulation G sustained the drug release for 10h which was the best and
showed non-fickian diffusion mechanism.
Kumar35 et. al in 2013 developed bilayered tablet containing Pioglitazone HCl
for immediate release using cross Povidone (super disintegrant) and Metformin
HCl for sustained release using poly ethylene oxide as matrix forming agent.
35
Formulation F5 exhibited first order release and diffusion was the dominant
mechanism for drug release.
Sahoo36 et. al in 2013 prepared Metformin HCl matrix tablets by wet granulation
technique using HPMC and Xanthan gum. HPMC alone couldn’t retard the drug
release for 12h but with Xanthan gum it gave satisfactory release profile. Short
term stability studies were performed for best formulation.
Charulatha et.al37 in 2012 prepared sustained release matrix tablets of
Acebrophylline (200mg) by wet granulation technique using HPMC K 100M with
Sodium CMC of various concentrations. Dissolution profile showed that as
polymer ratio increased, the release was retarded in the prepared matrix tablets
with different polymers.
Hadi et.al38 in 2012 had described about sustained release tablets of
Montelukast sodium prepared by direct compression method using various
polymers. The drug release was extended for a period of 12 h. The kinetic
treatment showed that the release of drug followed first order models. There
was no significant change in drug content after stability studies for optimised
formulation.
Potnuri et.al39 in 2012 prepared Diltiazem HCl bi-layered matrix tablets using
natural polymer (Gum olibanum) and hydrophilic polymer HPMC and
investigated the effect of binders (Starch, Gelatin PEG 6000), diluents and fillers
influencing drug release. The release rate of drug from matrices were affected
36
by an increase in the binder concentration except gelatin. Most dissolution
profiles followed zero order than first order and higuchi model.
Kamlesh et al40 in 2011 prepared Metformin HCl matrix tablet using different
pH dependent polymers like eudragit L100 and S100 and pH independent
polymers like eudragit RLPO and RSPO. Tablets were prepared by direct
compression. Exepients used didn’t react with the ingredients in the tablet which
was confirmed by FTIR studies. In vitro dissolution data’s were fitted into various
kinetic models. Korsmeyers peppas data’s revels that it followed diffusion along
with erosion.
Nanjwade et.al41 in 2011 developed oral extended release matrix tablet using
a combination of hydrophobic and hydrophilic polymers. They prepared the
tablets by two techniques such as direct compression and melt granulation
technique and evaluated their release characteristics and found that the melt
granulation technique was more effective in retarding the release than direct
compression and followed closely to korsmeyers peppas mechanism with a
correlation coefficient of 0.991.
Bangale et.al42 in 2011 made an attempt to formulate sustained release matrix
tablets of Nimodipine using various natural matrix former gums like xanthan
gum, olibanum gum and locust bean gum separately. Majority of designed
formulations displayed nearly zero order release. Korsmeyer and Peppas
equations gave release patterns of R =0.9925 and n=0.6054 respectively
indicating non-fickian or Anomalous types of diffusion through matrix of Locust
37
bean gum. The results demonstrated the feasibility of natural gum in the
development of matrix tablets for controlled delivery of nimodipine.
RajaSekharan et.al43 in 2011 formulated HPMC based controlled release
matrix tablets of theophylline with varying drug- polymer ratios (1:1 and 1:2).
The results indicated that high drug- polymer ratio (1:2) and hardness value (7
kg/cm2), prolonged the drug release rather than the low drug- polymer ratio.
(1:1). Release kinetics followed korsmeyers-peppas model and the mechanism
of drug release was by non-fickian.
Gupta et.al44 in 2011 prepared sustained release tablets (F1 to F4) using
different drug and polymer ratios by direct compression method .Polymers like
Sodium carboxymethyl cellulose (Sod.CMC), hydroxyl propyl methyl cellulose
(HPMC K100), Xanthan gum and HPMC K4 were used. In vitro dissolution study
was carried out for 16 h using paddle method in phosphate buffer (pH 6.8) as
dissolution media. Among all the formulations, F6 showed 100.42% of drug
release at the end of 16 h. This finding revealed that above a particular
concentration of Sod. CMC, HPMC K100 and xanthan gum were capable of
providing sustained drug release.
Samal et.al45 in 2011 prepared matrix tablet by wet granulation method using
hydrophilic Sodium CMC, HPMC, Eudragit‐L155, and Xanthan gum alone or in
combination with hydrophobic polymer ethyl cellulose. The release kinetics was
analysed using Zero order, First order, Higuchi and Hixson Crowell and that
presence of sodium CMC gave zero‐order release kinetics and the linearity
38
ranged from 0.990 to 0.996, with good drug entrapment efficiency ranging from
96 to 106% of drug.
Uner et.al46 in 2011 developed hydralazine HCl matrix tablet to overcome its
side effects and to enhance the bioavailability. They formulated matrix tablets
using different polymers (HPMC, carbomer, glyceryl dibehenate and Cetyl
alcohol) at various concentrations. Among these the slowest release was
obtained by carbomer followed by HPMC. Prepared tablets followed higuchi
kinetic model and non fickian drug release mechanism.
Rahman et.al47 in 2011 formulated sustained release matrix tablets of
Ronolazine by using Eudragit L 100-55 and different grades of HPMC (Methocel
E50 and Methocel K15M). Study showed that an increase in the polymer
concentrations resulted in a decrease of drug release.
Rojas et.al48 in 2011 designed a study using a simplex centroid experiment with
over 69 runs from which best combination of some hydrophilic polymers were
taken which extended the release of drug up to 24 h. The data were fitted to
korsmeyers- peppas model as it gave the best fit. A cubic model predicted best
release of Metformin HCl i.e., up to 24 h by combination of polymers such as
PVP, EC, HPMC, carrageenan, calcium alginate and gum arabic. Confirmation
of cubic model was done by validation.
Amish et.al49 in 2011 studied the effect of various polymers and additives.
Various ratio of polymers were taken and the water uptake study data indicated
that HPMC K100M containing tablets swelled higher than the additives present
39
in the tablet. Soluble and insoluble additives present in the tablets affected
release of the drug from HPMC K100M polymer. From the dissolution data it
was clear that starch showed better drug extending release among other
insoluble additives whereas SLS had a dramatic drug delaying property among
soluble additives.
Chandira et.al50 in 2010 formulated Metformin HCl extended release tablets
using different combination of polymers such as HPMC K100M and Carbopol
71 G with wet granulation (PVP K30) technique. The tablets were subjected to
physical and chemical evaluations and there were no significant changes
observed. In vitro dissolution studies were carried out and F10, considered as
optimised batch, gave a satisfactory release as that of innovator.
Ganesh et.al51 in 2010 prepared sustained release Diclofenac sodium matrix
tablets using cashew nut tree gum HPMC and Carbopol. In vitro release studies
were conducted for twelve h which stated that an increase in the polymer
concentration retarded the release of the drug to a great extent.
Shankar et.al52 in 2010 prepared modified release ciprofloxacin HCl matrix
tablets using different polymers. In vitro dissolution data showed that formulation
containing chitosan and guar gum in the ration of 2:1 (F6) showed 93.6%
release after 12 h whereas those containing lactose in the concentration of 50
and 75% (F7 & F8) showed 96.15% and 99.90% release after 12 h respectively.
Dixit et.al53 in 2009 prepared once daily matrix tablets of Metformin HCl by wet
granulation technique using non aqueous solvent as granulating agent
40
(isopropyl alcohol containing PVP K30) and polymers such as HPMC and locust
bean gum. Tablets were subjected to in vitro dissolution studies and results
indicated that formulation M5 containing HPMC and locust bean gum in the
ration of 200:30 could extend the release of tablets up to 8 h.
Nair et.al54 in 2009 prepared controlled release uncoated tablet by direct
compression method using various grades of HPMC (K100M and K4M) with a
hydrophilic drug enalapril maleate. Results showed that both the polymers alone
were enough to retard the release of drug from the tablet and gave higher r2
values for Higuchi and zero order release. Hence they concluded that HPMC
alone could retard the release of drug for 14 h.
Rao et.al55 in 2009 developed water soluble Tramadol HCl matrix tablet using
HPMC and natural polymers like Karaya gum and carrageenan. Tablets were
subjected to in vitro dissolution studies and data were fitted into different kinetic
models; it was observed that matrix tablet containing HPMC and carrageenan
successfully retarded the release of drug up to 12 h. DSC and FTIR studies
revealed that there was no interaction between the drug and exepients.
Thapa et.al56 in 2008 made Indomethacin containing matrix tablets using
different grades of HPMC (HPMC K4M, HPMC K15M, and HPMC K100M) and
were compared with marketed products. The dissolution profiles of formulations
containing different viscosity grades of HPMC in same concentrations were
different. The dissolution profile of developed formulations were compared with
41
marketed products and showed similarity with a similarity factor of 74.59 and
68.04.
Abdelkader et.al57 in 2007 developed Baclofen matrix tablets containing 25 mg
with different types and levels of polymers such as methylcellulose, sodium
alginate and carboxymethylcellulose. Among these, methylcellulose and sodium
alginate containing formulations showed high drug release retarding efficiency
and good reproducibility. These were stable when stored for 6 months in
ambient room condition which suggested that methylcellulose and sodium
alginate are good candidates for preparing modified release baclofen tablet
formulations.
42
2.1. Drug profile
2.1.1 Metformin HCl58
Fully synthesised and found to reduce blood sugar in 1920.
First described in scientific literature in 1922 by Emil Werner and James
bell
In 1957 French physician Jean Sterne published the first clinical trial
report of Metformin HCl as a treatment for diabetes.
Metformin HCl in synthesised using reaction of dimethyl amine
hydrochloride (dicyandiamide) and 2 – cyanoguanidine which are dissolved in
toluene with cooling to make a concentrated solution and an equimolar amount
of hydrogen chloride is slowly added59. When the mixture begins to boil at its
own, it is cooled and Metformin HCl precipitates with a yield of 96%.
Metformin HCl is an antidiabetic drug belonging to biguanide class which
is a first-line drug of choice for the treatment of type 2 diabetes. Particularly
given to obese patients with overweight (reduces LDL Cholesterol, triglycerides
and doesn’t cause weight gain) and normal kidney function 60. It is further
indicated in the treatment of polycystic ovary syndrome and has been
investigated for other diseases where insulin resistance is an important factor.
It is the only drug supressing the cardiovascular complications of diabetes. From
2010 onwards it is only one among two oral antidiabetics in the World Health
Organisation Model List of Essential Medicines (other being Glibenclamide).
43
Table 2. 1 : Parameters of Metformin HCl
2.1.2 Mechanism of action61
Metformin decreases hyperglycaemia primarily by suppressing glucose
production by the liver (hepatic gluconeogenesis). Metformin improves glucose
tolerance in type 2 diabetic patients. Its pharmacological mechanism of action
is different from other class of drugs. Metformin decreases
Hepatic glucose production
Intestinal glucose absorption and also
Improves insulin sensitivity by increasing peripheral glucose uptake and
utilisation.
Unlike sulphonylureas Metformin doesn’t produce hypoglycaemia and
hyperinsulinemia with normal and diabetic subjects. With Metformin therapy
Properties
Molecular Formula C4H11N5 Chemically Molar weight 129.16 g/mol Log P 1.254
Pharmacokinetics Bioavailability 50-60%
Cmax 1-3 H of Immediate release
4-8 H of Extended release
Tmax 1-3.1 H Route of administration Oral Elimination half life 6.2 H Excretion Renal (unchanged) Plasma protein binding Negligible Steady state reaches 1-2 days
44
insulin secretion remains unchanged hence decreased fasting insulin levels and
day-long plasma insulin response.
2.1.3 Dosage and administration
Given as 1000-2000 mg daily in one or divided doses. Starting dose one
tab/day, after 10-15 days with slow increase of dose. The maximum
recommended daily dose of Metformin HCl, USP is 2550 mg in adults and 2000
mg in paediatric patients (10 to 16 years of age). Metformin HCl, should be given
in divided doses with meals. Metformin HCl, should be started at a low dose,
with gradual dose escalation, both to reduce gastrointestinal side effects and to
permit identification of the minimum dose required for adequate glycaemic
control of the patient.
2.1.4 Adverse effects
GI- Nausea, vomiting, diarrhoea, anorexia, abdominal pain or cramps,
flatulence, colitis inducing pseudomembranous colitis.
Genitourinary: Pyuria, renal function impairment, dysuria, reversible
intestinal nephritis, haematuria, toxic nephropathy.
Haematological: Eosinophilia, neutropenia, lymphocytosis, decreased
platelet function, aplastic anaemia, haemorrhage.
Pregnancy: Category B
Lactation: Excreted in milk.
Lactic acidosis: A rare but serious complication that can occur due to
Metformin accumulation during treatment with Metformin. When it occurs
45
it is fatal in 50% of cases. It is characterised by increased blood lactate
levels (>5 mmol/L).
2.1.5 Contraindications
Renal disease or renal dysfunction.
Congestive heart failure requiring pharmacological treatment.
Known hypersensitivity to Metformin HCl.
Chronic or acute metabolic acidosis including diabetic ketoacidosis which
should be treated with insulin.
2.1.6 Precautions
Metformin should be temporarily discontinued in patients undergoing
radiologic studies involving intravascular administration of iodinated contrast
material, as this may result in acute alteration of renal function hence lactic
acidosis.
2.1.7 Identification test for Metformin HCl (I.P)
A. Determined by IR absorption spectrophotometry (2.4.6). Compare the
spectrum with that obtained with Metformin HCl RS or with the reference
spectrum of Metformin HCl.
B. Dissolve 25 mg in 5 ml of water , add 1.5 ml of 5 M sodium hydroxide, 1
ml of 1- naphthol solution and drop wise with shaking, 0.5 ml of sodium
hypochlorite solution (3% Cl); an orange red colour is produced which
darkens on keeping.
46
C. Dissolve 10 mg in 10 ml of water and add 10 ml of a solution prepared by
mixing equal volumes of a 10% w/v solution of potassium ferricyanide and
a 10% w/v solution of NaOH and allowing to stand for 20 minutes; a wine
red colour develops within 3 minutes.
D. Gives reaction A of chlorides (2.3.1).
E. Melts between 222°C and 226°C, Appendix 8.8
2.1.8 Assay
Weigh accurately about 60 mg, dissolve in 4 ml of anhydrous formic acid
and add 50 ml of acetic anhydride. Titrate with 0.1M perchloric acid, determine
the end point potentiometrically (2.4.25). Carry out a blank titration.
2.1.9 Packaging and storage
It is preserved in tight container at a temperature not exceeding 25°C
and protect from light and moisture.
47
POLYMERS PROFIE
2.2 Methocel62 2.2.1 Synonym: Hypromellose. 2.2.2 Nomenclature
METHOCEL is a trademark of The Dow Chemical Company for a line of
cellulose ether products. An initial letter identifies the type of cellulose ether, its
“chemistry.” “A” identifies methylcellulose (MC) products. “E,” “F,” and “K”
identify different hydroxypropyl methylcellulose (HPMC) products. METHOCEL
E and METHOCEL K are the most widely used for controlled-release drug
formulations. The number that follows the chemistry designation identifies the
viscosity of that product in millipascal-seconds (mPa·s), measured at 2%
concentration in water at 20°C. In designating viscosity, the letter “C” is
frequently used to represent a multiplier of 100, and the letter “M” is used to
represent a multiplier of 1000. Several different suffixes are also used to identify
special products. “P” is sometimes used to identify METHOCEL.
These cellulose ethers are water-soluble methyl cellulose and hydroxyl propyl
methyl cellulose polymers. They are derived from the pine pulp, the most
abundant polymer in nature, and used as thickeners, binders, film formers, and
for water retention. They are also used as suspension aids, protective colloids
and emulsifiers.
Does the job of two or more ingredients in many applications.
Delivers optimum performance at a lower concentration than required by
other water soluble polymers.
Peerless range of product types and performance.
48
Viscosity grades range from 15 to over 200,000 mPas for optimum
thickening, binding, moisture retention and other properties.
HPMC polymers are very versatile release agents. They are non-
ionic, so they minimize interaction problems when used in acidic, basic, or other
electrolytic systems. HPMC polymers work well with soluble and insoluble drugs
and at high and low dosage levels. And they are tolerant of many variables in
other ingredients and production methods.
2.2.3 Preparation
The cellulose obtained from cotton linters and wood pulp are treated with
an alkali like NaOH to produce swollen alkali cellulose. The alkali cellulose is
then treated with chloromethane and propylene oxide due to which it gets
converted to methyl hydroxyl propyl ether of cellulose. The final product is then
purified and ground to powder or granules.
2.2.4 Shelf life: 3 years
2.2.5 Characteristics
It is a white, yellowish white or greyish-white powder, inert, odourless,
tasteless, non-ionic, hydrophilic polymer.
49
2.2.6 Solubility
It is practically insoluble in hot water, in absolute ethanol, acetone, ether,
and in toluene. It dissolves in cold water forming a colloidal solution.
2.2.7 Properties
Its physicochemical properties like solubility, glass transition temperature
and viscosity depend upon the ration of methoxy and hydroxyl propoxyl groups
and the molecular weights. Various grades of Methocel are available which differ
in viscosity and extend of substitution. The different grades can be identified by
a number indicative of apparent viscosity, in mPas of a 2% aqueous solution at
20°C.
2.2.8 Substitution
The major chemical differences are in degree of methoxyl substitution
(DS), moles of hydroxyl propoxyl substitution (MS), and degree of
polymerization (measured as 2% solution viscosity). There are four established
product “chemistries” or substitution types for METHOCEL products, defined
according to the combination of their percent methoxyl/DS and percent hydroxyl
propoxyl/MS.
50
2.3 Carboxy methyl cellulose63 - AVICEL®
2.3.1 Chemical family: Carbohydrate, Cellulose Derivative
Chemically CMC is a cellulose derivative with carboxymethyl groups (-
CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose
monomers that make up the cellulose backbone.
2.3.2 Molecular structure
2.3.3 Synonyms
Microcrystalline cellulose (MCC), cellulose gel, Sodium Carboxy
methylcellulose: Carboxy methylcellulose, Carboxy methyl ether, Sodium CMC,
Sodium salt, Cellulose gum
2.3.4 Functional category: Polymer for Tablets and Capsule.
Table 2. 2 : Physical and chemical properties of Avicel
Odour Odourless
Appearance Off-white, free flowing powder
Percentage volatile Approx. 4% by weight
pH 6.0 - 8.0 (in solution)
Solubility in water Dispersible
Specific gravity (H2O = 1) Bulk Density, 0.6 g/cc
51
2.3.5 Stability and storage
It is a stable chemical substance. It should be stored in a well closed, air
tight container in a cool and dry place.
2.3.6 Application
Used as viscosity modifier or thickening agent to stabilise emulsions. It is
used as lubricant in non-volatile eye drops. It is used in controlled release matrix
formulation.
52
2.4 Cellulose acetate64
2.4.1 Synonym
Cellacephate, Cellulose acetate, Cellulosi acetas phthalas, Cellulose
acetate monopthalate, Acetylphthalylcellulose.
2.4.2 Introduction
Cellulose is a natural polymeric polysaccharide composed of β-D-glucose
subunits. Hydroxyl groups of cellulose can be modified chemically to form esters
or ethers that differ in physicochemical properties allowing for a wide range of
applications. This is an enteric coating polymer which withstands prolonged
contact with acidic gastric fluids, but dissolves readily in the mildly acidic to
neutral environment of the small intestine. It can be applied to tablets or granules
from solutions of organic solvent.
2.4.3 Molecular structure
2.4.4 Synthesis
The most common way to prepare cellulose acetate phthalate consists of
the reaction of a partially substituted cellulose acetate (CA) with phthalic
anhydride in the presence of an organic solvent and a basic catalyst. The
53
organic solvents widely used as reaction media for the phthaloylation of
cellulose acetate are acetic acid, acetone or pyridine. The basic catalysts
employed are anhydrous sodium acetate when using acetic acid, amines when
using acetone, and the organic solvent itself when using pyridine as reaction
medium.
Table 2. 3: Physical and chemical properties of Cellulose acetate
2.4.5 Applications
1. Used in enteric coating of tablets and capsules.
2. Matrix binder for tablets and capsules.
2.4.6 Storage
Stable for several years if stored in a cool, dry place. Keep container
closed when not in use. Store in a tightly closed container. Store in a cool, dry,
well ventilated area away from incompatible substances.
2.4.7 Stability
Stable under normal temperature and pressure.
Appearance White to off white powder
Odour Faint, characteristic
Molecular weight 2534.12 g/mol
Molecular formula C116H116O64
pH solubility ≥6.2
Viscosity cP at 25ºC 68
Specific Gravity (H2O = 1)1.08
54
2.5 Magnesium stearate
2.5.1 Synonym
Magnesium octadeconate, Octadeconate acid magnesium salt, stearic
acid magnesium salt.
2.5.2 Chemical name Octadecanoic acid magnesium salt.
2.5.3 Functional category
Tablets and Capsules lubricant.
2.5.4 Description
It is fine, white, precipitated or milled, impalpable powder with low bulk
density. Insoluble in water, powder shows a faint odour of Stearic acid, tasteless.
The powder is greasy to touch and readily adhere to skin.
2.5.5 Application in formulation
1. Used extensively in cosmetic formulations (barrier creams), food and
pharmaceutical industry.
2. Primarily used as lubricant in tablets and capsules in a concentration of
0.25 – 0.5%.
2.5.6 Stability and storage
It is a stable chemical substance. It should be stored in a well closed, air
tight container in a cool and dry place.
55
2.5.7 Incompatibilities
It is incompatible with strong acids, iron salts and should not be mixed
with strong oxidising agents. It should not be included in the formulations
containing aspirin, some vitamins and most of the alkaloidal salts.
Safety: It is one of the mostly used pharmaceutical excipient as it is nontoxic
when ingested through oral route. When consumed in large amounts produces
laxative effect and can irritate mucosal layer of GIT.
56
2.6 Aerosil65
2.6.1 Synonym Aerosil 200, amorphous fumed silica.
2.6.2 Chemical name Silicon dioxide.
Table 2. 4: Physical and chemical properties of Aerosil
Odour Odourless
Taste Tasteless
Molecular weight 60.08 g/mol
Colour White
pH 4
Loss on Drying ≤ 1.5
Melting point 1610ºC (2930ºF)
Specific gravity 2.2 (Water = 1)
2.6.3 Storage
Keep container tightly closed. Keep container in a cool, well-ventilated
area. Do not store above 23ºC (73.4ºF).
2.6.4 Application
1. Used as glidant to improve the flow property of granules.
2. Used to stabilise emulsions.
3. Thickening and suspending agent in gels and semisolids.
57
NEED FOR THE STUDYCHAPTER 3
58
3. NEED FOR THE STUDY
Metformin is a first line drug of choice for the treatment of type II diabetes
which act by decreasing hepatic glucose output and peripheral insulin
resistance. It can be given to obese patients with overweight having normal
kidney function. The conventional therapy has the following drawbacks:
1. Relatively short half-life of 1.5 to 4.5 h.
2. High dose of 1.5 to 2.0 g/day with conventional therapy.
3. Single 500mg gives a bioavailability of 50 – 60%.
4. High incidence of GI side effects such as abdominal discomfort, nausea
and diarrhoea (up to 30%) which particularly occurs in the early 3 weeks
of treatment.
5. Food delays the Tmax of drug up to 35 min.
6. Reduced patient compliance due to increased dosing frequency.
By formulating the drug in controlled release system, GI side effects had
reduced considerably as reported by Harry Howlett66 and also a decrease in
dosing frequency increases patient compliance. So, it was decided to formulate
it in a controlled release dosage form. Although there are marketed formulation
available Glycomet SR 500mg was taken for comparison, which works under
the diffusion controlled release mechanism. This system has certain limitations
such as
High cost of production,
High molecular weight drugs are difficult to deliver and
59
Dose dumping chances are high.
Incomplete drug release
In order to overcome the following limitations of the marketed formulation a new
formulation should be developed. By developing such a formulation the
advantages are:
1. Reduction in dose can be achieved which can reduce the toxic side
effects of conventional release systems
2. High incidence of GI side effects can be reduced
3. Patient compliance can be improved
Disadvantage:
1. Despite of the following advantage of the new formulation the drug itself
is having a rare side effect of lactic acidosis, which cannot be eliminate
by any type of formulation.
60
OBJECTIVES AND HYPOTHESISCHAPTER 4
61
4. OBJECTIVES AND HYPOTHESIS
Primary objective of the study was:
1. To study the effect of different ratios of polymers and its drug release
properties in a swelling restricted matrix tablet of Metformin HCl.
2. To develop a swelling restricted matrix tablets of Metformin HCl using
different ratios of polymers.
3. To optimize the formula.
4. To compare the in vitro studies like dissolution, disintegration, swelling
index etc. of developed formulation with marketed product
5. To perform bio equivalence study of newly developed formulation and
compare it with marketed formulation (Glycomet SR).
This could be achieved by:
1. Formulating and evaluating controlled release matrix tablets of Metformin
HCl, as this type of formulation can achieve therapeutically effective
concentration of drug in the systemic circulation over an extended period
of time. This type of formulation will eliminate the above said issues and
will exhibit additional advantages such as low cost, simple processing,
improved efficacy, reduces adverse effects, flexibility in terms of range of
release profiles, increased convenience and patient compliance.
2. Formulating Metformin into a controlled release formulation using various
hydrophilic polymers like HPMC (K4M, K15M and K100M) in different
ratios, with hydrophobic polymer CMC to act as a release modulator.
62
Finally the best formulation selected to give partial coating with cellulose
acetate (swelling restricted matrix tablets) to further control the release.
63
METHODOLOGYCHAPTER 5
64
6. METHODOLOGY
5.1 Preformulation studies67, 99:
Preformulation studies are conducted before the development of any
formulations as it is necessary to find out drug characteristics and its stability in
the formulation.
Description: Drug was visually inspected for any change of colour, odour,
etc. as specified in the quality certificate.
Melting point: Capillary method was selected for determining the melting
point. The test was performed in triplicate.
Solubility in dissolution media: Screw caped glass vials of 20 ml capacity
were taken and filled with 10 ml of media (i.e. simulated gastric fluid pH-
1.2, simulated gastric fluid, pH-6.8, and simulated intestinal fluid, pH-7.4).
Drug was added to this till saturation occurred and shaken at room
temperature for 48 h. After that, samples were filtered, appropriately
diluted and analysed at 233nm using UV visible spectrophotometer.
5.1.1 Drug excipient compatibility studies98:
These studies are conducted prior to formulation development, to
determine the physicochemical properties, drug-excipient compatibility, etc. To
establish drug-excipient compatibility, drug alone was first taken and then the
mixture of powder and excipients were taken in 1:1 ratio. The sample was
ground in a mortar and filled in vials, sealed with rubber stoppers and stored for
a period of 2 weeks at 60ºC (except for Mg stearate for which 40ºC is used) and
65
the same samples were retained for 2 months at 40ºC. After storage the drug
was observed physically for liquefaction, caking, odour and gas formation and
discolouration. Further FTIR characterization was done for drug excipient
compatibility.
5.1.1.1 FTIR characterization 68: The desired drug concentration was checked
by assaying the sample; pellets were prepared by mixing with KBr and
scanned. The IR spectrum of drug was recorded using Shimadzu FTIR
Spectrophotometer with scanning range at 250-4500 cm-1.
5.1.1.2 Differential scanning calorimetry (DSC) 69: DSC analysis were
conducted in order to evaluate possible solid-state interaction between
the components and consequently to assess the actual drug excipient
compatibility. Physical mixtures were prepared (Pure Metformin HCl and
F14) dried and examined using DSC (Mettler Toledo DSC 822) to find
its thermal behaviour. Samples are dried thoroughly and placed in an
aluminium sealed pan and preheated to 200ºC. Samples were cooled to
room temperature and reheated from 40ºC to 450ºC at a scanning rate
of 10ºC/min.
5.1.1.3 Powder X-ray diffraction 69: Pure drug Metformin HCl and its physical
mixture with exepients (Metformin HCl, HPMC K100M and CMC) were
subjected to PXRD studies. The crystalline behaviour of pure Metformin
HCl and formulation blend containing Metformin HCl and exepients
66
(HPMC K100M and CMC) were studied using instrument Bruker AXS
D8 Advanced, scanning was done up to 2θ of 70º.
5.2 Pre-optimisation studies. 5.2.1 Optimisation of polymer concentration.
For fixing the desired range of variables (polymer concentration) required
for the final formulation, a pre-optimisation study was conducted with different
concentration of polymers. As the concentration of polymers changed there was
a direct effect on swelling index and drug release.
Tablets were prepared using concentration of polymers form low to high
in each batch. HPMC different grades and CMC were used as polymers for
retarding the drug release. Micro crystalline cellulose was used as filler as the
tablets were prepared by direct compression. Talc and Magnesium stearate
were used as lubricant and glidant.
5.3 Formulation development: 5.3.1 Preparation of matrix tablets of Metformin HCl
Metformin HCl (500mg) matrix tablets were prepared by mixing the drug
with various concentrations of polymers (shown in Table 5. 1) such as HPMC
(various grades), CMC and other excipient’s like micro crystalline cellulose,
magnesium stearate, talc etc. in a polythene bag. Tablets were prepared by
direct compression technique for which prepared powder blend was sieved
through sieve no 40 and dried in a hot air oven below 60ºC. Powder blend was
then mixed with magnesium stearate and aerosil to get it lubricated, which was
then compressed into tablets in a rotary tablet compression machine using 12
mm caplet punches. Before compression the surfaces of the dies and punches
67
were lubricated with magnesium stearate. Prepared tablets were stored in an
airtight container at room temperature for further studies.
5.3.2 Preparation of 5% Cellulose acetate (CA) film:
To 100ml of acetone, 5g of cellulose acetate was gradually added. After
all the cellulose acetate was added the solution was stirred for 2 h to completely
dissolve the CA. The CA solution was degassed for 3 h and it is ready for
coating.
5.3.3 Preparation of swelling restricted matrix tablets:
Swelling restricted matrix tablets were prepared by giving the tablet a
partial coating with 5% cellulose acetate solution. Different levels of coating
were given as shown in Figure 1.5, by dipping the tablet into the solution for
three times. MFH 13 was coated on both of the crown portions of tablets (Figure
1.5 C) whereas MFH 14 was coated only on one of the crown of tablets (Figure
1.5 A).
68
Table 5. 1: Composition of matrix tablets containing Metformin HCl.
Sl. No Ingredients MFH 1 MFH 2 MFH 3 MFH 4 MFH 5 MFH 6 MFH 7 MFH 8 MFH 9 MFH10 MFH11 MFH12 Batch 1 Batch 2 Batch 3 Batch 4
1 Metformin HCl 500 500 500 500 500 500 500 500 500 500 500 500
2 HPMC K4M 150 200 250 X X X X X X X X X
3 HPMC K15M X X X 150 200 250 X X X X X X
4 HPMC K100M X X X X X X 150 200 250 200 150 125
5 CMC X X X X X X X X X 50 100 125
6 MCC 200 150 100 200 150 100 200 150 100 100 100 100
8 Mg Stearate q.s q.s q.s q.s q.s q.s q.s q.s q.s q.s q.s q.s
9 Aerosil q.s q.s q.s q.s q.s q.s q.s q.s q.s q.s q.s q.s
Total Weight (mg) 850 850 850 850 850 850 850 850 850 850 850 850
69
5.4 Evaluation of prepared tablets:
5.4.1 Pre formulation studies 5.4.1.1 Bulk density 70:
Loose bulk density
An accurately weighed quantity of powder was transferred to a 10 ml
measuring cylinder and the volume occupied by the powder in terms of ml
was recorded.
Weight of powder in gm Loose bulk density (LBD) =
Volume packed in ml
Tapped bulk density
Loosely packed powder in the cylinder was tapped 100 times on a
plane hard surface and volume occupied in ml was noted.
Weight of powder in gm Tapped bulk density (TDB) =
Tapped volume in ml 5.4.1.2 Hausner’s ratio 71:
It is the number that is related to the flowability of powder or granules.
A Hausner’s ratio of <1.25 indicates a powder that is free flowing whereas >1.25
indicates poor flow ability.
Hausner’s ratio = TDB / LDB
5.4.1.3 Carr’s compressibility index 72:
It is an indication of the compressibility of a granule or powder. In
pharmaceutics it is an indication of flowability of powder. A Carr’s index with
value more than 25 is considered to be an indication of low flowability and less
70
than 25 is having good flow property. The smaller the Carr’s Index the better the
flow properties. For example 5-15 indicates excellent, 12-16 good, 18-21 fair
and > 23 poor flow.
Carr’s index (%) = [(TBD – LBD) x 100] ÷ TDB
Table 5. 2: Scale of flowability of powders
Compressibility index (%) Flow description 5 -15 Excellent 12-16 Good 18-21 Fair 23-28 Poor (Very fluid powder) 28-35 Poor (Fluid cohesive powder) 35-38 Very poor ˃40 Extremely poor
5.4.1.4 Angle of repose70:
A funnel is fixed and is secured with its tip at a height (h) of 2cm above
graph paper which is placed on a horizontal surface. The powder is dropped
and the radius (r) is measured. Angle of repose can be measured by the
following equation
ϴ = tan-1 (h/r) or Tan ϴ = h / r
Values ≤ 30 indicates free flowing powder and 30 ≥ 40 are poor flowing powders.
Table 5. 3: Angle of repose and corresponding flow property
Angle of repose (θ) Flow property ˂25 Excellent
25-30 Good 31-40 Passable (may hang up) 41-50 Poor (must agitate, vibrate) ˃50 Very poor
71
5.4.2 Evaluation of physical properties of matrix tablets:
5.4.2.1 Thickness and diameter 71, 100
10 tablets were randomly picked from each batch and their thickness
and diameter were measured using a calibrated dial Vernier calliper (± 5% is
allowed).
5.4.2.2 Weight variation test 72, 100
20 tablets were randomly selected from each batch and weighed on
an electronic balance. Weight of 10 tablets and individual tablets were taken;
their mean and standard deviation of weight were calculated from each batch.
Table 5. 4: Maximum allowable deviation for tablets
5.4.2.3 Hardness test 73, 99
10 tablets were randomly selected from each batch and hardness of
each tablet was determined by using a Pfizer type hardness tester. Mean of
standard deviation was calculated for each batch.
5.4.2.4 Friability test 74, 100
It is the ability of tablets to withstand mechanical shocks during
handling and transportation. 10 tablets were selected randomly from each batch
and weighed and placed in a friability test apparatus and operated at a speed of
25 rpm for 4 minutes. Tablets were collected and weighed again. The loss of
Average weight of tablet (mg)
Maximum percentage deviation allowed (%)
130 mg or less ± 10.0 130 – 324 ± 7.5
˃ 324 ± 5
72
tablet weight was calculated and measured in terms of % friability. Acceptable
value of friability is less than 1.
F = [(WINITIAL – WFINAL) x 100] ÷ WINITIAL
5.5 Swelling index of matrix tablets 75
The swelling property of matrix tablets was measured in terms of
percentage weight gain by the tablet. The swelling behaviour of all formulations
were studied. One tablet from each formulation was kept in a petridish
containing pH 7.4 phosphate buffer. At the end of 0.5 h and 1h, the tablets were
withdrawn and soaked with tissue paper, then weighed. Then after each hour,
weight of tablets were weighed and continued till 8h percentage weight gain of
tablets were calculated by the formula
S.I = {(Mt – Mo) / Mo} x 100
Where, S.I = swelling index, Mt = weight of tablet at time t (h), Mo = weight of
tablet at zero time.
Fig 5. 1 : Tablet immersed in dissolution media for swelling index study
73
5.6 Drug content estimation 76:
a) Standard solution: 100mg of pure Metformin HCl (drug) was dissolved in
water in a volumetric flask and the volume was made up to the mark and
sonicated for 5 minutes.
b) Sample solution: 20 tablets from each batch were randomly selected and
weighed accurately and finely powdered. To a powder equivalent to
100mg of Metformin HCl about 70ml of water was added and dissolved
with the aid of shaker for 15 minutes; then sufficient quantity of water was
added to produce 100ml in a volumetric flask, mixed well and filtered. To
1ml of the filtrate methanol was added to produce 100ml and mixed well.
The absorbance of the resulting solution was measured at 233nm using
standard solution as blank. This test was conducted in triplicate.
5.7 In vitro release studies:
5.7.1 Preparation of standard curve for Metformin HCl77:
Preparation of standard stock solution:
Accurately weighed 100mg of Metformin HCl and transferred into a 100ml
volumetric flask, dissolved in 50ml of distilled water and made up to to obtain a
standard stock solution of 1000µg/ml drug concentration. From this Standard
stock solution of Metformin HCl, 100µg/ml (Stock Solution) was prepared by
pipetting 10 ml of stock solution to a 100ml volumetric flask and making up to
100ml with distilled water.
74
Determination of wavelength of maximum amplitude (D2 value) of
Metformin HCL.
10ml of the above solution was diluted to 100ml with the same solvent to
get 10µg/ml of concentration. The UV spectrum of final solution was scanned in
the range of 200 – 400 nm against distilled water as blank. The λmax was found
at 233.8 nm.
STD Curve of Metformin HCl
One mille litre (1ml) of the standard stock solution was taken and diluted
to 10ml with distilled water (100µg/ml), from the above solution 0.2, 0.4, 0.6, 0.8
and 1 ml were pipetted out and diluted to 10 ml with distilled water to get the
final concentration of 2, 4, 6, 8 and 10µg/ml respectively.
5.7.2 In vitro drug release studies78, 79.
Fig 5. 2 : Type I Dissolution apparatus used for study
75
In vitro release studies of prepared matrix tablets and marketed
(Glycomet SR) were conducted for a period of 12 h using an eight station USP
XXII type I apparatus (Fig 5. 2) at 37±0.5ºC; speed of basket was set at 100±1
rpm. In each flask 900ml buffered media (pH 6.8) was used as dissolution
media.
An aliquot (5ml) was withdrawn at every 1 h interval and replaced with fresh
medium to maintain sink condition. Samples were filtered through whatman filter
paper no.1 and diluted appropriately and analysed at 233nm by double beam
UV / visible spectrophotometer using dissolution medium as blank. Experiments
were performed as: n = 3. The amount of drug present in the samples was
calculated by using calibration curve constructed from reference standard.
5.8 RELEASE KINETIC MODELS.
RELEASE MECHANISM OF DRUG
While developing novel drug release system it is essential to understand
the drug release mechanism. There are various types of drug release
mechanisms such as zero order, first order, higuchi model and peppas model.
The most appropriate model is selected by fitting the data into the following
mathematical models and finding which model gives the best fit to them.
5.8.1 Zero-order treatment 80
Zero order takes place at a constant rate independent of existing
concentration or initial concentration. This system is used to describe drug
dissolution of several modified release pharmaceutical dosage forms such as
76
transdermal systems and sustained release tablets (osmotic and matrix) with
low soluble drugs. This model can be expressed as
Qt = Q0+K0t
Where, Qt = Amount of drug released in time (t). Q0= Initial amount of drug in solution, K0= Zero order release constant.
5.8.2 First-order treatment 81
The application of this model was first introduced by Gibaldi and Feldman
(1967) and later by Wagner in (1969). First order treatment takes place at a
constant proportion of drug concentration available at that time so that the
process is depending on the initial concentration. The following equation is used
to express this model.
Log c = Log c0 – kt / 2.303
Where, c = amount of drug remaining unreleased at time t. C0= initial amount of drug in solution. K = first order rate constant.
5.8.3 Higuchi’s model 82
This model was used to study the release of water soluble and low soluble drug
incorporated in semisolid and solid matrices. The following equation is used to
express the model.
Qt = kt1/2
Where, Qt = amount of drug released in time t K = Higuchi’s constant.
A linear relationship between amount of drug released (Q) versus square root
of time (t1/2) is observed if the drug release from the matrix is diffusion controlled.
77
5.8.4 Korsmeyer – Peppas model 83, 84
Kosermeyer in 1983 developed a simple and semi empirical model
relating exponentially the drug release to elapsed time. If diffusion is the main
drug release mechanism, a graph representing the drug amount released
versus square root of time gives a straight line. Under certain experimental
conditions the release mechanism deviated from ficks equation follows an
anomalous behaviour (non fickian). In such condition the following equation is
generally used.
Mt / Minf = atn
Where, Mt / Minf = fraction release of drug. a = constant depending on the structural and geometric characteristics of the drug dosage form. n = release exponent.
Peppas used this ‘n’ value to characterise different release mechanisms.
The value of n indicates the drug release mechanism.
Interpretation of diffusion release mechanisms
Table 5. 5: Value of ‘n’ with corresponding drug release mechanism
Release Exponent ‘n’ Mechanism of drug transport
< 0.5 Fickian transport
0.5< n < 1.0 Non – Fickian Transport
1.0 Case II transport
> 1.0 Super case II transport
78
For cylinder:
n = 0.45 instead of 0.5 and 0.89 instead of 1.0.
This model is used to analyse the release of drug from polymeric dosage forms,
when the release mechanism is not understood or when there is a possibility of
using more than one type of release mechanisms.
5.9 SIMILARITY FACTOR 85, 101
Similarity factor (f2) is a logarithmic reciprocal square root transformation
of the sum of squared error and is a measurement of the similarity in percentage
(%) dissolution between two curves. To evaluate and compare dissolution data,
the dissolution data are statistically analysed using dissolution similarity factor.
Similarity factor can be found out by using the following equation
Where,
n = number of dissolution time points.
Wt = Optional weight factor.
Rt = Reference dissolution point at time t.
Tt = Test dissolution point at time t.
The f2 factor between 50 and 100 suggests that the dissolution is similar
and the f2 values ranging from 100 suggest that the two dissolution profiles are
similar, whereas the smaller values suggest that they are not similar.
79
5.10 STATISTICAL ANALYSIS 102:
Statistical analysis was performed using Minitab software on the
experimental data and the data obtained from regression analysis are shown
below.
5.11 STABILITY STUDIES 86, 87:
It is defined as “the capacity of a drug product to remain within the
specifications established to ensure its identity, strength, quality, and purity”. It
can be simply explained as the ability of a drug to resist deterioration”.
Short-term stability study: Was performed at temperature 40 ± 2ºC over
a period of three months on the matrix tablet (MFH 14). Sufficient number of
tablets (10) were packed in amber colored screw capped bottles and kept in
stability chamber maintained at 40 ± 2ºC. Samples were taken at one month
interval for drug content estimation. At the end of three months, tablets were
evaluated for drug content, percentage friability, swelling index and dissolution
test to determine the drug release profiles.
Long-term stability study: Was performed at a temperature of 25 ± 2ºC
60% ± 5% RH over a period of twelve months on the matrix tablet (MFH 14).
Sufficient number of tablets (10) were packed in amber colored screw capped
bottles and kept in stability chamber maintained at 25 ± 2ºC. Samples were
taken at 0, 3, 6, 9 and 12 month interval for drug content estimation. On each
specified interval tablets were evaluated for drug content, percentage friability,
swelling index and dissolution test to determine the drug release profiles.
80
Table 5. 6: Conditions as per ICH Guidelines
5.12 In vivo studies 5.12.1 Pharmacokinetics studies 5.12.1.1 Blood Sample Collection
Three groups of Rabbit, each comprising of three, were used for the
pharmacokinetic analysis. Each rabbit of all the groups were given 400 mg/kg
of drug.
Table 5. 7: Treatment of different formulations to various groups of rabbit
Group Treatment
A STD Drug solution of Metformin HCl (p.o)
B Marketed tablet of Metformin HCl (p.o)
C Sustained Release F14 tablet formulation (p.o)
The rabbits were acclimated with laboratory conditions for one week.
Before pharmacokinetic study, all the rabbits were fasted overnight. At zero
hour 1 ml of blood sample was collected from marginal ear vein of each animal
and this was considered as blank. No food or liquid other than water was
permitted until 4 h following administration of product (normal t1/2 of drug 2 h).
Blood samples were collected at 0.5,1, 2, 3, 4, 6, 8, 16, and 24 h intervals from
marginal ear vein into heparinized centrifuge tubes.
Study Storage condition
Minimum time Temperature Relative humidity %
Long term 25ºC ± 2ºC 60% ± 5% RH 12 Months
Intermediate 30ºC ± 2ºC 65% ± 5% RH 6 Months
Accelerated 40ºC ± 2ºC 75% ± 5% RH 3 Months
81
5.12.1.2 Plasma samples extraction
For spiked samples as well as animal blood plasma sample, the following
earlier procedure was used for HPLC analysis to extract Metformin HCl. 100 µl
of Metformin HCl solution of appropriate concentration and 100 µl of Glipizide
solution (5 µg mol-1) were added to 900 µl of drug free plasma contained in a
clean 5 ml Ria vial properly mixed (for spiked samples). After centrifugation at
3000 rpm for 15 minutes, 700 µl of the supernatant was evaporated to dryness
at 45o C under nitrogen. The residue was reconstituted in 100 µl of mobile phase
and 20 µl of this was injected to HPLC system (Shimadzu LC-10AT with SPD-
10A detector).
5.12.1.3 Method Validation of Metformin HCl in HPLC system88
Instead of developing a new method, the already reported method was
used for Metformin HCl in plasma level. According to this method, HPLC using
C18 ODS (5 μ) 250 × 4.60 mm column, mobile phase selected for this method
contained acetonitrile: phosphate buffer (65:35) pH adjusted to 5.75 with o-
phosphoric acid which was filtered through 0.2 μ membrane filter. Flow rate
employed was 1.0 ml/ min. Detection of eluent was carried out at 233.0 nm.
Glipizide was used as the internal standard. Column was saturated with mobile
phase for about an hour at the above specified conditions. HPLC method was
used for validation of specificity, linearity and range, precision, accuracy,
robustness and solution stability according to USP and ICH guidelines.
After setting the chromatographic conditions the instrument was stabilized
to obtain a steady base line and a mixed standard dilution of pure drug
82
containing 10 μg/ml of Metformin HCl and 5 μg/ml of glipizide (internal standard)
were prepared in mobile phase, filtered through 0.2 μ membrane filter and
loaded in the injector of instrument fitted with 20μl fixed volume loop. The
solution was injected three times and the chromatogram recorded. The mean
retention time for Metformin HCl and glipizide were found to be 2.30 and 3.95
min, respectively.
Standard stock solutions of Metformin HCl and glipizide with a
concentration of 100 μg/ml was prepared separately in the mobile phase. For
the preparation of drug solutions for the calibration curve, aliquots of standard
stock solution of Metformin HCl (0.25, 0.5, 1.0, 1.5, 2.0 and 2.5 ml) were
transferred into a series of 10 ml volumetric flask and to each flask 0.5 ml of
glipizide standard stock solution was added and the volume made up to the
mark with mobile phase. Each solution was injected after filtration through 0.2 μ
membrane filter and a chromatogram was recorded. The calibration curve was
plotted between concentration of drug and ratio of peak area of Metformin HCl
and Glipizide (internal standard). Linearity was found to be in a concentration
range of 0 to 25 μg/ml of Metformin HCl with linear regression equation as y=
0.0204x+0.0012 and the correlation coefficient value of 0.9990.
After setting the chromatographic conditions and stabilizing the
instrument, the formulated sample solution was injected and a chromatogram
was recorded. The injection was repeated three times and the peak area of
Metformin HCl and Glipizide were recorded. The peak area ratio of drug to
internal standard was calculated and the amount of drug present was estimated
83
from the respective calibration curve. The analysis of formulated tablet was
compared with the commercially available tablet formulation of Metformin HCl.
5.12.2 Pharmacodynamic studies 5.12.2.1 Induction of Diabetes 89
Diabetes mellitus (DM) was induced by a single intravenous (IV) injection
of Alloxan monohydrate (150 mg/kg, body wt.), dissolved in 0.1 M sodium citrate
buffer (pH 4.5). Only vehicle (citrate buffer, 1 ml/kg) was given to fasted-alloxan
treated rabbits80. In order to reduce the death rate due to hypoglycaemic shock,
alloxan-treated rabbits received 5% of glucose instead of water for 24 h after
diabetes induction (Barbosa et al., 2008).Hyperglycaemia was confirmed by
elevated glucose levels in plasma, which was determined at 72 h, following 7th
day after injection (stabilization period). The threshold value of fasting plasma
glucose to diagnose diabetes was taken as >200mg/dl. Only rabbits having this
blood glucose levels were used for the study.
5.12.2.2 Experimental design
Rabbits used for experiments were divided into groups of 6 animals each.
Table 5. 8: Experimental Design for Pharmacodynamic studies in rabbit
Group Treatment
I Diabetic rabbits - given only Alloxan (150 mg/Kg, i.p.)
II Diabetic rabbits treated with Standard Tablet(p.o)
III Diabetic rabbits treated with Formulation Tablet (p.o)
84
5.12.2.3 Administration of drugs
On day one (01), fasted-treated rabbits were administered with standard
and test tablets through intragastric tube and this was repeated for three
consecutive days (1-3) ( orally) and fasted alloxan treated rabbits were given
vehicle only (citrate buffer, 1 ml/kg).
5.12.2.4 Blood Sample Collection and determination of blood glucose
At the end of the 3rd day of drug treatment, blood was collected from
marginal ear veins with the help of sterilized needle and syringe, at 0h, 2nd h, 3rd
h, 4thh, 6thh, 8thh, and 10th h and transferred into the appropriate sterilized micro
centrifuge tube. The blood was used to determine Fasting blood glucose (FBG)
level.
5.12.2.5 Body weight
Body weight of animals in each group was recorded on 0,7th and 14th day
and difference in weight were noted.
85
RESULT AND DISCUSSIONCHAPTER 6
86
6. RESULTS AND DISCUSSIONS
6.1 Preformulation studies Description: Visual inspection of the drug was done.
Table 6. 1: Result of visual inspection of Metformin HCl
Property Observation Organoleptic
properties A white crystalline powder, without any characteristic
odour
Melting point: was found to be in the range of 222ºC to 226ºC
Solubility of drug in different media:
Table 6. 2: Solubility of Metformin HCl in different media
Solvent Solubility (mg/ml)
Distilled water 145
SGF (pH-1.2) 256
SIF (pH-6.8) 282
SIF (pH-7.4) 156
6.2 Compatibility studies FT-IR: The compatibility study of Metformin HCl was carried out using FT-
IR spectrum. The IR spectra of pure drug and drug polymer mixtures (1:1) are
given in figures
Fig 6. 1, Fig 6. 2, Fig 6. 3 and Fig 6. 4. Figures shows qualitative
identification for Metformin HCl. FT-IR characterisation indicated that no
interactions of drug were observed neither with exepients nor with additives.
This is comparable to a study done by Kamlesh J et . al in 2011 confirmed in
their study that excipients didn’t react with the ingredients.
87
Fig 6. 1 : FT-IR peak of different functional groups of Metformin HCl
88
Fig 6. 2 : FT-IR peak of different functional groups of Metformin HCl and HPMC K4M
89
Fig 6. 3 : FT-IR peak of different functional groups of Metformin HCl and HPMC K15M
90
Fig 6. 4 : FT-IR peak of different functional groups of Metformin HCl and HPMC K100M
91
DSC: Has been used to measure the amount of heat energy absorbed
(endothermic) or released (exothermic) by the drug when it is heated or cooled.
The thermal curve of Metformin HCl showed an initial flat profile followed by a
sharp endothermic peak representing the melting of the substance in the range
of 223 - 237ºC. The thermal curves of both mixtures obtained by simple blending
gave a superimposition as that of single component indicating the absence of
solid-state interaction as shown in Fig 6.5. A similar study was conducted by
Raghavendra Rao N et al in 2009 prepared Tramadol HCl matrix tablet revealed
Fig 6. 5: DSC of pure Metformin HCl (a), Physical mixture of Metformin HCl with HPMC K100M, Physical mixture of Metformin HCl with HPMC K100M and CMC.
92
PXRD: Solid substances are usually characterised as either crystalline or
amorphous state. Spacing of atoms or molecules in crystals are of repetitious
spacing whereas in amorphous form they are randomly placed which is similar
to liquids. Amorphous forms are of higher thermodynamic energy than the
crystalline form due to random arrangement of atoms and molecules hence the
energy required for separation is low, so their solubility and dissolution rates are
higher.
The physical mixture of formulation drug peak was observed with varying
intensity. This suggests that in the formulation drug remains in crystalline form
and it doesn’t transform into amorphous state (Fig 6.6).
Fig 6. 6: X-ray diffraction studies of pure Metformin HCl and formulation blend containing Metformin HCl, HPMC K100M and CMC.
93
6.3 Pre-optimisation studies
6.3.1 Optimisation of polymer concentration
Matrix tablets of Metformin HCl were prepared in each batch using
different concentration of polymers i.e. from lower to higher concentration. The
formulated tablets were evaluated for its swelling index and drug release at Q2,
Q8 and Q12.
The concentration of polymers and its effect on response variables helped
to fix the higher and lower concentration of polymers. The higher concentration
of various grades of HPMC were selected as it gave more controlled release of
drug with sufficient swelling index and drug release at Q2, Q8 and Q12 h. among
batch 1, batch 2 and batch 3, MFH9 was selected as it gave the desired release
and swelling index pattern when compared to others. Batch 4 was prepared by
using a combination of HPMC K100M and CMC in order to reduce the burst
release at Q2 interval. This results can be compared with R. Charulatha et al in
2012, which states that HPMC K100M with Na CMC was effective in retarding
the release as the polymer ratio increased.
6.4 Design and preparation of swelling restricted matrix tablet of
Metformin HCl
Tablets from Batch 4 (MFH 12) were selected as they met the fixed
parameters of release and swelling index. This formulation was converted to
swelling restricted matrix tablet by partially coating them with 5% cellulose
acetate solution. By doing so, there swelling was restricted and hence release
was further retarded and also no studies were found in literature to compare it.
94
6.5 Evaluation of flow properties of powder
Powders prepared for direct compression method were evaluated by
measuring the following parameters such as bulk density, angle of repose,
Hausner’s factor, compressibility index, and drug content. The results are shown
in Table 6. 3.
Angle of repose: The result of angle of repose (<30) indicate good flow
properties and the values for prepared formulations ranges from 21.59 –
26.37.
Hausner’s factor: The values of Hausner’s factor were under satisfactory
range.
Compressibility index: the values up to 15% results were in good to
excellent flow properties and values of all formulations ranges from 17.29
– 20.60%.
Drug content: the values of all the formulations were in the range from
97.48% - 99.83%.
All these results obtained indicated that the granules possessed satisfactory
flow properties, compressibility, and uniform drug content.
95
Table 6. 3: Values of pre – compression parameters of developed formulations, n = 3
Sl.No LBD (gm/cc)
TBD (gm/cc)
Hausner’s Factor
Carr's compressibility Index (%)
Angle of repose (º)
MFH 1 0.4244 0.5345 1.26 20.60 21.59±0.012
MFH 2 0.4156 0.5126 1.23 18.92 23.52±0.013
MFH 3 0.4136 0.5164 1.25 19.91 26.37±0.021
MFH 4 0.4247 0.5135 1.21 17.29 22.74±0.026
MFH 5 0.4275 0.5274 1.23 18.94 23.93±0.069
MFH 6 0.4172 0.5164 1.24 19.21 25.49±0.010
MFH 7 0.4225 0.5203 1.23 18.80 21.73±0.040
MFH 8 0.4394 0.5428 1.24 19.05 25.30±0.062
MFH 9 0.4199 0.5194 1.24 19.16 22.38±0.042
MFH 10 0.4291 0.5273 1.23 18.62 24.28±0.064
MFH 11 0.4315 0.5349 1.24 19.33 22.66±0.055
MFH 12 0.4174 0.5158 1.24 19.08 25.44±0.028
96
6.6 Evaluation of tablets
6.6.1 General appearance
The formulated tablets were evaluated for its organoleptic characteristics
as shown in Table 6. 4.
Table 6. 4: Observational report of various parameters of tablets
Parameters Observation
Shape All tablets remained in caplet shape with no visible cracks.
Colour Off white
Odour No characteristic odour
Appearance All tablets were elegant in appearance
6.6.2 Hardness Normally for oral tablets the hardness range is in between 5 – 10 kg/cm2.
Hardness of the tablets were tested using Pfizer type hardness tester and the
results are shown in Table 6. 5. Hardness of all the tablets were within the
acceptable limit i.e. from 5.23 kg/cm2 – 5.87 kg/cm2. Hence all the formulated
tablets pass the hardness test.
6.6.3 Thickness
All formulated tablets were evaluated for uniformity of thickness using a
Vernier calliper and the results are shown in Table 6. 5. The thickness of all the
formulated tablets were in the range of 3.20 ± 2.00 mm which indicated that all
the tablets were of uniform thickness.
97
6.6.4 Weight variation test
The test was performed as per the official method. Twenty tablets from
each batch were selected randomly and individually weighed. Each tablet was
evaluated for percentage deviation and their results are shown in Table 6. 5.
Allowable percentage deviation for prepared tablets are ±5 % for weight more
than 324 mg. and the results showed that all were within the acceptable limits.
6.6.5 Friability test
The apparatus used for conducting friability test was Roche friabilator.
Pre-weighed 10 tablets were taken and loaded into the apparatus and the
revolution speed was adjusted to 100. After 100 revolutions the tablets were
dusted and reweighed. The results are shown in Table 6. 5. The acceptable
weight loss for tablets should not be more than 1% of the weight of tablets. The
friability of all tablets were within the prescribed limits, which showed that there
was a good adhesion property between the excipients used in the formulation.
6.6.6 Drug content
The percentage content of Metformin HCl in the formulation was
estimated at 234 nm using spectrophotometer. The limit for content uniformity
should be in the range of 90 – 110% and the results showed that content
uniformity of Metformin HCl in the formulation was between 97.48 ± 0.54 – 99.83
± 0.72% (Table 6. 5), which is within the acceptable limits.
All the formulation in batches from MFH1 – MFH 12 showed values within
the specified limits for all test and hence complying with pharmacopoeial
specifications indicating that all prepared tablets were of standard quality.
98
Table 6. 5: Results of post-compression parameters
Batch Hardness Thickness %
Friability Weight
variation % Drug content
MFH 1 5.23 3.40 0.8 860.54 99.83
MFH 2 5.44 3.60 0.75 870.67 98.45
MFH 3 5.57 3.80 0.64 854.98 99.38
MFH 4 5.27 3.50 0.56 848.63 99.68
MFH 5 5.47 3.70 0.58 859.3 97.48
MFH 6 5.50 3.50 0.64 855.37 98.37
MFH 7 5.30 3.60 0.65 851.84 99.25
MFH 8 5.50 3.40 0.59 862.75 98.57
MFH 9 5.50 3.50 0.54 847.85 99.73
MFH 10 5.87 3.60 0.63 857.83 98.49
MFH 11 5.60 3.50 0.68 860.37 99.28
MFH 12 5.63 3.70 0.53 854.48 99.63
6.7 Swelling index study
Swelling index study was performed on all batches for a period of 2 h to
12 h. From the result of this evaluation test it was observed that there was a
linear relationship between swelling index and concentration of polymer till 8 h
which was due to the formation of a viscous gel type mass. Afterwards the gel
mass got eroded or dissolved in the media from the outermost layer of tablet.
The results of swelling index study are shown in Table 6. 6.
99
Fig 6. 7: Shows the swelling index of the formulations from MFH1 – MFH14
Fig 6. 8: Swelled tablet in SGF while conducting swelling index study.
0
10
20
30
40
50
60
70
80
90
100
0 2 4 6 8 10 12 14
% S
WEL
LIN
G IN
DEX
TIME
Swelling Index
MFH1 MFH2 MFH3 MFH4 MFH5 MFH6 MFH7
MFH8 MFH9 MFH10 MFH11 MFH12 MFH13 MFH14
100
Fig 6. 9: Tablets formed gel like mass when conducting swelling index study
101
Table 6. 6: Showing results of % swelling index value of all formulations.
Time In Hours % Swelling Index
MFH1 MFH2 MFH3 MFH4 MFH5 MFH6 MFH7 MFH8 MFH9 MFH10 MFH11 MFH12 MFH13 MFH14
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
2 40 42 43 41 44 45 42 44 41 44 41 47 26 20
4 49 52 55 52 56 58 51 55 51 53 53 59 34 29
6 57 60 64 58 62 66 59 60 63 64 71 76 52 41
8 82 85 87 81 84 88 83 84 84 81 82 88 65 59
10 74 75 75 73 71 77 74 76 82 73 76 91 75 66
12 64 66 72 66 69 70 69 71 74 68 72 85 68 61
102
6.8 In vitro dissolution studies
6.8.1 Preparation of calibration curve
Calibration curve of Metformin HCl was plotted with concentration in x-axis and
absorbance in y-axis (Fig 6.10).
Table 6. 7: Absorbance values of Metformin HCl in distilled water.
Concentration (µG/ML) Absorbance at 234nm 2 0.1915 4 0.4186 6 0.5465 8 0.7371
10 0.9155
Fig 6. 10: Calibration curve of Metformin HCl in distilled water
y = 0.0906x + 0.0152R² = 0.9963
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12
Ab
sorb
ance
Concentration
Metformin HCl STD Curve
Absor
Linear (Absor)
103
6.9 In vitro drug release studies:
The results of cumulative percentage of drug release are given in the
Table 6. 8 and Table 6. 9 which clearly indicated that the release rate and
percentage drug release showed a wide variation. From the obtained result it
was understood that the drug release was strongly affected by the concentration
of polymer in the formulation (Fig 6. 13). The matrix tablet during swelling is an
aggregate mass of water swollen polymer, drug and excipients which
experiences various degree of hydration. The solid content in the tablet of
various regions varied from 0 – 100%. The area of 100% solid was just a wetted
mass of powder. When the water content of wetted mass increased the polymer
became hydrated and formed a gel. In the outermost layer the polymer had no
structural integrity and hence got eroded.
Fig 6. 11: Tablet removed at Q2 interval form dissolution study
104
Formulations fabricated with different grades of HPMC alone i.e. MFH1 –
MFH 9 showed an initial burst release but release was retarded by increasing
the concentration of polymer, which may be due to the formation of a thick
viscous gel layer around the tablet. Among these formulations (MFH 1 – MFH
9), the best formulation i.e. MFH 9 was selected and treated with combination
of HPMC K100M and CMC in different ratios (MFH 10 – MFH 12), which resulted
in a decrease in the initial burst release and hence a more retarding effect was
observed. From MFH 10 – MFH 12 formulations MFH 12 was selected as there
was a decrease in the drug release, particularly at Q2 H interval and was
converted to swelling restricted matrix tablet (MFH 13 & MFH 14), where the
release was more effectively retarded to the desired frequency.
Comparative results of optimised formulation and marketed formulation
are shown in Fig 6.14.
Fig 6. 12: Performing dissolution test in type I apparatus
105
Table 6. 8: In Vitro %CDR of drug from Metformin HCl matrix tablets MFH 1 to MFH 7 (n = 3)
Time in h MFH1 MFH2 MFH3 MFH4 MFH5 MFH6 MFH7
1 45.00±0.577
34.07±0.581
27.00±0.635
42.74±0.491
25.64±0.670
25.07±0.581
26.63±0.591
2 59.20±0.325
41.25±0.557
31.44±0.694
48.47±0.664
42.02±0.578
32.28±0.582
40.05±0.580
3 62.09±0.550
46.55±0.652
40.58±0.462
56.38±0.665
48.45±0.557
41.21±0.532
52.08±0.583
4 67.49±0.550
53.05±0.580
46.78±0.665
62.46±0.559
57.09±0.585
46.65±0.614
59.07±0.581
5 71.09±0.550
61.15±0.522
58.48±0.580
70.36±0.560
62.81±0.724
57.52±0.553
63.31±0.701
6 76.56±0.606
54.82±0.318
62.06±0.580
76.21±0.723
70.77±0.722
63.02±0.578
69.11±0.587
7 83.70±0.665
71.64±0.664
66.56±0.580
78.06±0.581
75.12±0.590
71.06±0.580
71.40±0.401
8 87.26±0.696
76.09±0.585
71.06±0.580
81.40±0.666
79.51±0.609
77.33±0.668
74.17±0.639
9 90.93±0.521
80.78±0.434
80.06±0.617
84.40±0.723
83.35±0.486
81.03±0.578
82.43±0.705
10 97.90±0.458
87.05±0.580
86.26±0.617
93.31±0.724
89.03±0.578
85.46±0.638
90.48±0.640
11 98.03±0.469
91.63±0.611
90.73±0.536
97.51±0.701
95.21±0.645
91.60±0.680
94.31±0.667
12 98.25±0.531
97.10±0.586
96.53±0.811
98.45±0.476
98.32±0.562
94.43±0.669
97.66±0.599
106
Table 6. 9: In vitro %CDR of drug from Metformin HCl matrix tablets MFH8 to MFH14, (n = 3)
Time in h MFH8 MFH9 MFH10 MFH11 MFH12 MFH13 MFH14
1 23.30±0.723
22.20±0.917
25.07±0.581
21.40±0.700
22.30±0.700
20.73±0.433
18.32±0.610
2 39.28±0.676
33.03±0.578
37.44±0.747
36.77±0.754
36.01±0.577
34.07±0.582
31.31±0.701
3 51.08±0.583
36.09±0.584
49.21±0.740
48.22±0.646
40.38±0.583
38.85±0.522
39.48±0.525
4 55.59±0.621
47.98±0.591
54.82±0.725
53.05±0.580
46.95±0.580
47.61±0.552
45.81±0.725
5 61.56±0.617
54.89±0.948
61.09±0.584
59.19±0.641
58.52±0.405
60.28±0.550
58.03±0.578
6 68.11±0.588
61.86±0.940
65.66±0.810
65.03±0.611
64.32±0.439
66.07±0.581
66.07±0.582
7 74.17±0.639
69.32±0.659
70.12±0.611
71.78±0.755
68.32±0.496
71.06±0.580
74.62±0.554
8 77.78±0.722
72.41±0.463
72.03±0.578
75.12±0.589
73.80±0.724
75.53±0.611
80.06±0.581
9 82.42±0.741
76.43±0.869
76.33±0.704
80.66±0.882
78.08±0.583
79.09±0.585
83.11±0.588
10 87.16±0.617
79.09±0.585
81.03±0.578
89.03±0.578
84.11±0.588
85.56±0.549
91.20±0.643
11 93.26±0.655
82.42±0.712
85.46±0.696
93.73±0.722
91.00±0.577
89.07±0.581
92.77±0.722
12 97.05±0.580
89.70±1.193
90.10±0.635
95.17±0.601
93.50±0.529
91.80±0.723
94.70±0.723
107
Fig 6. 13 : In vitro dissolution profile of Metformin HCl matrix tablet.
0.00
20.00
40.00
60.00
80.00
100.00
120.00
0 2 4 6 8 10 12 14
Mea
n %
CD
R
Time
MEAN % CDR Vs TIME
MFH1 MFH2 MFH3 MFH4 MFH5 MFH6 MFH7
MFH8 MFH9 MFH10 MFH11 MFH12 MFH13 MFH14
108
Fig 6.14: In vitro dissolution profile of Glycomet SR and Formulation F14
6.10 Release kinetic model:
To find out the drug release from the obtained data, all the data were fitted
into various kinetic models such as zero order, first order and higuchi model.
Linear regression analysis was done for all the batches and their results are
shown in the following Table 6. 10. The higuchi square root of time model had
the higher r2 values which when compared to zero order and first order kinetic
models showed that they followed higuchi model.
Further, to understand the drug release mechanism, the data were fitted
in to peppas model and the obtained ‘n’ values indicated the drug transport
mechanism. From the obtained data for peppas model, ‘n’ values were within
the range of 0.5 < n < 1.0 as shown in Table 6. 10, which clearly indicated that
the drug release followed non – fickian anomalous transport diffusion
mechanism which is comparable to a study done by T. Raja Sekharan et al in
2011 explained released kinetic followed korsmeyers peppas model and
mechanism of drug release was non-fickian for the preparation of HPMC based
controlled release matrix tablet.
0.00
20.00
40.00
60.00
80.00
100.00
120.00
1 2 3 4 5 6 7 8 9 10 11 12
Con
cent
ratio
n
Time
Glycomet SR Vs F14
Glycomet SR F14
109
Table 6. 10: Correlation coefficient values and release kinetics of Metformin HCl matrix tablets
Formulation Zero order First order Higuchi model Peppas model
AVG k AVG r2 AVG k AVG r2 AVG k AVG r2 AVG n AVG r2 MFH 1 4.7751 0.9637 -0.3372 0.8951 0.2218 0.9851 0.3192 0.9818 MFH 2 5.6638 0.9961 -0.2394 0.8642 0.2605 0.9884 0.4367 0.9785 MFH 3 6.3877 0.9919 -0.2400 0.8709 0.2937 0.9836 0.5463 0.9771 MFH 4 5.0957 0.9788 -0.3068 0.8537 0.2365 0.9891 0.3568 0.9798 MFH 5 6.1117 0.9685 -0.2900 0.8588 0.2863 0.9967 0.5196 0.9936
MFH 6 6.4548 0.9845 -0.2262 0.9484 0.2992 0.9924 0.5679 0.9899 MFH 7 5.9096 0.9635 -0.2679 0.8669 0.2762 0.9873 0.5003 0.9888 MFH 8 6.0788 0.9619 -0.2519 0.8985 0.2854 0.9947 0.5421 0.9876 MFH 9 5.9328 0.9638 -0.1673 0.9762 0.2777 0.9908 0.5804 0.9902
MFH 10 5.2974 0.9507 -0.1634 0.9699 0.2498 0.9914 0.4920 0.9903 MFH 11 6.3020 0.9698 -0.2406 0.9281 0.2946 0.9942 0.5762 0.9894 MFH 12 6.2578 0.9810 -0.2106 0.9403 0.2908 0.9937 0.5722 0.9935 MFH 13 6.3349 0.9632 -0.2014 0.9800 0.2969 0.9926 0.6043 0.9920 MFH 14 7.0509 0.9647 -0.2537 0.9683 0.3300 0.9913 0.6765 0.9936
110
The Precompression and post compression in this study were evaluated
and were within acceptable limits. Data were fitted into various kinetic models
which was comparable to a study done by Mohammed Raquibul Hasan et al in
2014 for the preparation of ER Metformin HCl.
6.11 Stability studies:
Short term stability study: Accelerated stability studies were conducted
to prove how the manufactured tablets may change with respect to time under
the influence of environmental factors like temperature and humidity. As per the
guidelines, short term stability study was conducted for a period of 6 months (
Fig 6. 14) with temperature at 40 ± 2ºC and 75 ± 5% relative humidity. It
showed negligible changes in respect to appearance, drug content, dissolution
and assay. The obtained results are shown in table 6.11.
Optimised formulations are considered to be stable as they were considerably
stable even after the storage of 6 months and there was no change from the
initial assay of 5% or more. This confirmed that the formulations were stable
during the stability study period.
Table 6. 11: Results of short term stability study of MFH14
Evaluation MFH 14 SF14 Colour Off white No change
Drug content % 99.63 ± 0.53 99.56 ± 0.48
Swelling index Q2 (h) Q8 (h) Q2 (h) Q8 (h)
20.0% 58.82% 21.2% 58.67%
Hardness 5.63 5.60
Friability 0.53% 0.60%
111
Fig 6. 14 : Dissolution profile of MFH 14 Vs SF14 (formulation after stability study)
Long Term Stability Study: As per the guidelines, long term stability
study was conducted for a period of 12 months (Fig 6.15) with temperature at
25 ± 2ºC and 60 ± 5% relative humidity. It showed negligible changes in respect
to appearance, drug content, dissolution and assay. The obtained results are
shown in.table 6.12. Optimised formulations are considered to be stable as they
were considerably stable even after the storage of 12 months and there was no
change from the initial assay of 5% or more. This confirmed that the formulations
were stable during the stability study period. A similar studies was found in the
literature by Abdelkader H et al in 2007 and Mohammed Abdul Hadi et al in 2012
found that there were no significant changes in drug content after stability
studies for optimised formulation.
0.0
20.0
40.0
60.0
80.0
100.0
120.0
1 2 3 4 5 6 7 8 9 10 11 12
Co
nce
ntr
atio
n
Time
SHORT TERM STABILITY STUDY
MFH 14
SF14
112
Table 6. 12: Results of Long term stability study of MFH14
Fig 6. 15: Dissolution profile of MFH 14 after long term stability study
6.12 Similarity factor:
Similarity factor of formulation MFH14 when compared with reference
formulation was 70.228.
Evaluation 0 Month 12 Month Colour Off white No change
Drug content % 99.63 ± 0.53 95.56 ± 0.47
Swelling index Q2 (h) Q8 (h) Q2 (h) Q8 (h)
20.0% 58.82% 22.6% 60.15%
Hardness 5.63 5.85
Friability 0.53% 0.84%
0
20
40
60
80
100
120
0 2 4 6 8 10 12 14
Co
nce
ntr
atio
n
Time
Long Term Stability Study
0 Month 3 Month 6 Month 9 Month 12 Month
113
6.13 In vivo release studies
6.13.1 Pharmacokinetic study of Metformin HCl
Overnight fasted rabbits were treated with standard drug (Group A),
marketed formulation (Group B) and MFH 14 formulation (Group C). Blood
samples were collected, plasma extraction was done, method was validated and
the obtained data were plotted with time along y – axis and concentration of
drug in plasma along x – axis. Fig 6. 16 is showing the graph of standard drug,
marketed formulation and MFH14 formulation which was administered to the
animal. From the graph it is understood that the MFH 14 formulation can
effectively maintain the blood plasma level up to 24 h which is more than the
marketed formulation.
Fig 6. 16: Comparative Plasma level of Metformin HCl in Rabbits
-1
-0.5
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20 25 30
Co
ncn
etr
atio
n
Time
Plasma Concnetration Vs Time
Reference STD Marketed MFH 14
114
6.13.2 Pharmacodynamic study of Metformin HCl
After the injection of alloxan for inducing diabetes in healthy rabbits the
following stages were observed.
1. Within few minutes of alloxan injection a sudden hypoglycaemic phase
was observed, which lasted for 20 minutes of onset of hypoglycaemic
stage.
2. After one hour of administration of alloxan an increase in the
concentration of blood glucose level was observed. This hyperglycaemic
phase lasted for 2 – 4 h.
3. After 4 – 8 h of alloxan injection again hypoglycaemic stage was
developed which persisted throughout the study.
After the 3rd stage it was confirmed that alloxan had induced pancreatic
beta cell toxicity which formed diabetogenicity in the alloxan treated rabbits.
Before injecting alloxan, rabbits were orally administered with 2g of glucose /kg
body weight in 10 ml of distilled water. After injection of alloxan, rabbits were
stabilised for a period of 7 days, with free access to food and water. On the
seventh day all surviving diabetic rabbits were randomly tested for blood sugar
levels and the results were ranging from 200mg/dl to 650mg/dl, which confirmed
that all rabbits had developed type 2 diabetes, adequately required for the study.
115
Rabbits were divided into 3 groups and each group were treated
differently i.e. group A (standard drug), group B (MFH 14 Formulation) and
group C –control- (only alloxan). From the obtained data shown and plotted in
Fig 6. 17, MFH 14 formulation was effective in controlling the blood glucose level
in a more consistent and steady form, which clearly indicated that MFH14
formulation was effective in controlling diabetes rather than marketed
formulation.
Fig 6. 17 : Effect of MFH 14 formulation on alloxan induced rabbits
6.13.3 Effect of body weight on alloxan treated rabbits
Alloxan treated rabbits were divided in to 3 groups and treated with
standard formulation, MFH 14 formulation, and the last group was kept as
control. Weight of all the rabbits were taken from initial day up to 10 days of
treatment. From the obtained data it was observed that groups treated with
standard formulation and MFH 14 formulation had a marginal increase in the
25
6.6
7
28
2
27
2
25
6.3
3
21
6.6
7
15
8.3
3
12
8.3
3
26
7.5
25
4.2
5
21
7.7
5
20
1.7
5
19
2
18
3.2
5
14
4.7
5
32
0.6
7
36
7.5
45
6.6
7
34
2.6
7
33
4.3
3
31
9
29
0.3
31 2 3 4 5 6 7
PLA
SMA
GLU
CO
SE M
G/D
L
TIME (H)
PLASMA GLUCOSE VS TIME
Alloxan + STD Alloxan + MFH 14 Only Alloxan
116
body weight while the group that was kept as control had a marginal decrease
in the body weight (Fig 6. 188).
Fig 6. 18: Effect of new formulation on body weight.
Pharmacokinetic parameters were found by collecting blood samples
from marginal ear vein of rabbits, extraction of plasma, and method validation in
HPLC system (Fig 6. 199) and was compared with a marketed formulation as
shown in Fig 6. 16. From the obtained data it could be understood that MFH 14
formulation maintained plasma concentration for a period of 24 h. Hence it could
effectively control the release of Metformin from the formulation.
1.2
1.1 1
.151
.26
1.1
5
1.1
1.3
1.2
2
1.0
8
A L L O X A N + S T D A L L O X A N + M F H 1 4 O N L Y A L L O X A N
BO
DY
WEI
GH
T
GROUPS
GROUP VS BODY WEIGHTDay 0 Day 7 Day 10
117
Fig 6. 19: Chromatogram showing Metformin HCl and internal standard Glipizide
Table 6. 13: Pharmacokinetic parameters obtained from three different formulations of Metformin HCl in rabbits (using Residual method PK analysis)
Sl.No PK parameters Type of formulation
Reference STD solution
Marketed product
Formulated SR tablet
1 Cmax 2.2 ng/ml 1.4 ng/ml 1.2 ng/ml 2 Tmax 2 h 2 h 2 h
3 Elimination rate constant (Ke)
0.1388/h 0.0506/h 0.0455 /h
4 Absorption rate constant (Ka)
0.1524/h 0.6222/h 0.6284 /h
5 AUC0t 61.64 ng h/ml 7905.23 ng h/ml
9040.22 ng h/ml
6 Elimination half-life (t1/2)
0.5 h 13.69 h 15.23 h
7 Vd 6.45 litres 23.66 litres 25.85 litres 8 ClT 14.92 ml/min 19.95 ml/min 20.50 ml/min
118
6.14 Statistical analysis
Mathematical relationships for the measured dependent variable
(response) and the independent variables were developed using statistical
software, Graph pad. The two output variables (responses), such as Release
Time (R1) and percentage drug release (R2) were evaluated. The predicated
and actual values of the responses were calculated and found to be in good
agreement with experimental values.
From the t-test comparison of MFH 14 and marketed product,
calculated ‘t’ value was 0.0009. There was no difference between the MFH 14
and marketed formulations. The MFH 14 formulations were subjected to short
term stability studies, namely, for a period of 3 months as per ICH guidelines at
room temperature (25ºC ± 2ºC and 60% ± 5% RH) and accelerated conditions
of temperature and humidity, (40ºC ± 2ºC and 75% ± 5% RH) respectively for
finding the effect of ageing on release pattern. Both the release data were
subjected to t- test and the ‘p’ value was ˂ 0.0001 which was statistically very
significant. Hence there was no significant difference between the formulations.
Therefore MFH 14 can be taken as the best formulation. From the in vivo studies
of marketed and MFH 14 formulations ‘p’ value was 0.0016 which suggested
that they were statistically significant. There were no similar in vivo studies were
found in the literature to compare.
119
CONCLUSIONCHAPTER 7
120
7. CONCLUSION
In the present study an attempt was made to formulate and develop a
controlled release swelling restricted matrix tablet containing Metformin HCl
using various ratios of synthetic polymers. Initially chemical interactions were
found out using Fourier transform infrared spectrophotometer, Differential
scanning calorimetry and powdered X-ray diffraction technique. From the study
it was concluded that there was no chemical interaction between the drug and
the exepients used for the formulation of matrix tablets and at the same time the
drug existed in crystalline nature and didn’t changed to its amorphous form.
From the pre optimisation studies it could be concluded that lower and
higher concentration of polymers gave undesired release patterns. It helped in
fixing the ratio of polymers in final batches of formulations, which gave sufficient
swelling index and release patterns. The effect of different ratio of polymers
were studied and it clearly showed that the drug release rate for the entire batch
had a wide variation. The results clearly indicated that the drug release was
strongly affected by the polymers selected for the study.
The obtained pre compression and post compression study data revealed
that the prepared tablets comply with the requirements necessary to pass official
quality control test. The findings from the dissolution study revealed that
hydrophilic matrix tablet of HPMC K100M alone could not retard the release of
Metformin HCl as it gave an initial burst release at Q2 interval. This burst release
121
was controlled by combining with CMC which retarded the release rate of
Metformin HCl from the matrices and reduced the burst release at Q2 interval.
A slow and constant release was achieved by coating the best formulation (MFH
12) with cellulose acetate 5% solution and a swelling restricted matrix tablet was
developed. By converting to swelling restricted matrix tablet the release was
further retarded and the initial burst release at Q2 interval was controlled
effectively and the fixed parameters were achieved. Release kinetic models
revealed that drug release profiles of all formulations confirmed higuchi model
and followed non – fickian diffusion transport.
MFH 14 was taken as the optimised formulation where diffusion coupled
with erosion could be the mechanism for drug release which help to reduce the
frequency of administration and decrease the dose dependent side effects
associated with the repeated administration of Metformin HCl. Thus it can be
concluded that the prepared swelling restricted matrix tablets had the ability to
control the release of Metformin HCl from the formulation at a pre-determined
rate for a period of 12 h.
From the data of stability studies it could be concluded that the optimised
formulations were stable when they were stored for a period of 6 months (Short
term stability study) at a temperature of 40 ± 2ºC and 75 ± 5% humidity and 12
Months (Long term stability study) at a temperature of 25 ± 2ºC and 60 ± 5%
humidity.
122
The in vivo study of MFH 14 tablets were compared with marketed
formulation. The marketed formulation had certain disadvantages such as;
Glycomet had a diffusion controlled reservoir release mechanism which
works under the principle of diffusion and erosion, whose drawbacks are
high cost of production, more chances of dose dumping, incomplete
release and larger molecular weight drugs cannot be incorporated.
The newly developed formulation is a swelling restricted matrix tablet which
overcomes the above said drawbacks. The in vivo study conducted using rabbits
showed that these tablets were able to ensure controlled drug release for a
longer period and also it has the potential to lower the plasma glucose level.
Advantages of newly developed formulation:
Newly developed formulation is a matrix dissolution controlled system.
Hence it is easy to manufacture, its cost of production is low, low chance
of dose dumping and gives a complete release profile.
123
REFERENCESCHAPTER 8
124
8. REFERENCES
1. Tarun kumar guleri et. al. A review on mouth dissolving tablets.
International journal of medicinal chemistry and analysis, 2013; 3 (2): 57
– 65.
2. Tapaswi Rani Dash, Pankaj Verma. Matrix Tablets: An Approach towards
Oral Extended Release Drug Delivery. International Journal of Pharma
Research & Review, Feb 2013; 2(2): 12 – 24.
3. Chugh Isha et. al. Oral sustained drug delivery system: An overview.
International research journal of pharmacy, 2012; 3(5): 57 – 62.
4. Rajesh Z. Mujoriya. Formulation and evaluation of enteric coated pellets of
pantoprazole sodium by extrusion and spheronization method, [Internet] 2009.
Available from: http://www.pharmatutor.org/articles/formulation-and-evaluation-
of-enteric-coated-pellets-of-pentaprazole-sodium-by-extrusion-spheronization .
5. D.M.Brahmankar, Sunil B Jaiswal. Controlled release medication.
Biopharmaceutics and Pharmacokinetics A Treatise. Vallabh Prakashan;
Delhi, 398 – 399.
6. Modi Kushal et.al. Oral controlled drug delivery system: An overview.
International research journal of Pharmacy, 2013; 4(3): 70 – 76.
7. Navin Dixit et.al. Sustain release drug delivery system. Indian journal of
research in pharmacy and biotechnology, 2013; 1(3): 305 – 310.
125
8. Colloidal and surface phenomena: Pharmaceutical capsules and tablet
[Internet] 2004. Available from website
http://wwwcourses.sens.buffalo.edu/spring04/ce457_527/yoshiko
9. Gedar sushma et.al. An overview on techniques implemented for
sustained release matrix tablets of Glipizide. International journal of
advanced pharmaceutics, 2014; 4(2): 93 – 98.
10. Prakash pawan et.al. Role of natural polymers in sustained release drug
delivery system: Application and recent approaches. International
research journal of pharmacy, 2011; 2(9): 6 – 11.
11. A Goyal et.al. Factors influencing drug release characteristics from
hydrophilic polymer matrix tablet. Asian journal of pharmaceutical and
clinical research, 2009; 2(1): 93 – 98.
12. H. Omidian, K. Park. Swelling agents and devices in oral drug delivery
system. Journal of drug delivery science and technology, 2008; 18(2): 83
– 93.
13. Arvind Singh Rathode et.al. An overview: Matrix tablet as controlled drug
delivery system. International journal of research and development in
pharmacy and life science, 2013; 2(4): 482 – 492.
14. Colombo P et.al. Swelling controlled release in hydrogel matrices for oral
route. Advanced drug delivery review, 1993; 11: 37 – 57.
126
15. Kumar R V. Scope of biodegradable polymers for controlled drug delivery.
Drug development and industrial pharmacy, 2001; 27 (1): 1 – 30.
16. Popli H. Evaluation of sustained release formulation. The eastern
pharmacist, 1990; 33: 75 – 79.
17. Mathiowitz E. Encyclopaedia of controlled drug delivery. Wiley
intrescience publication, 1999; 1: 445.
18. Lian-Dong Hu et.al. Preparation and in vitro/in vivo evaluation of
sustained release Metformin HCl pellets. European journal of
Pharmaceutics and Biopharmaceutics, 2006; 64: 185 – 192.
19. Jo Young Gwan et.al. Metformin tablets with sustained release and
method for preparing the same. United States patent, 2007; 0275061A1:
1 -3.
20. Donald L. Wise. Drug release from swelling-controlled system. Marcel
Dekker In, 2005; 190 – 201.
21. Salsa. T. Oral controlled release dosage forms: Cellulose ether polymers
in hydrophilic matrices. Drug development and industrial pharmacy, 1997;
23(9): 929.
22. D.M.Brahmankar, Sunil B. Jaiswal. Controlled release medication.
Biopharmaceutics and Pharmacokinetics: A Treatise. Vallabh Prakashan,
2005; p 335.
127
23. Reddy K R, Mutalik S, Reddy S. Once-Daily sustained-release matrix
tablets of Nicorandil: Formulation and in vitro evaluation. American
Association of Pharmaceutical Scientist, 2003; 4(4): 61.
24. Higuchi W I. Diffusional models useful in biopharmaceutics drug release
rate processes. Journal of Pharmaceutical Sciences, 1967; 56: 315 – 324.
25. Noyes A A and Whitney W R. The rate of solution of solid substances in
their own solutions. Journal of American Chemical Society, 1897; 19: 930
– 934.
26. Lakshmi P K. Dissolution testing is widely used in the pharmaceutical
industry for optimisation of formulation and quality control of different
dosage forms, Pharmacinfo net 2010.
27. Korsmeyer R W, Gurny R, Doelker E, Buri P, Peppas N A. Mechanism of
solute release from porous hydrophilic polymers. International Journal of
Pharmaceutics, 1983; 15: 25 – 35.
28. Pamu Sandhya, Faheem Unnisa Begum, Afreen. Formulation and Evaluation of
Bilayer Tablets of Glimepiride and Metformin HCl. IOSR Journal of Pharmacy and
Biological Science, 2014; 9(1): 38-45.
29. Renati Damodar and Babji Movva. Preparation and In-vitro Evaluation of
Metformin HCl Tablets Containing Sustained Release Beads for Increasing
Therapeutic Window. Journal of bioequivalence and bioavailability, 2014; 6(3):
91-95.
128
30. G Sridhar Babu, D Vijay Kumar, M Aishwarya, P S Malathy. Formulation and in
vitro characterisation of sustained release matrix tablets of Metformin HCl.
Journal of Global Trends in Pharmaceutical Sciences, 2014; 5(14), 2085-2092.
31. Mohammad Raquibul Hasan, Md. Abul Hossen, Aumit Roy,Tufikul Islam and Md.
Saiful Islam Pathan. Preparation of Metformin HCl Extended Release Matrix
Tablets by Direct Compression Method and Its in vitro Evaluation. British Journal
of Pharmaceutical Research, 2014; 4(24): 2679-2693.
32. Dharmendra Solanki, Surendra kumar Jain, Sujata Mahapatra. Formulation and
evaluation of sustained release Metformin HCl tablet using natural
polysaccharide. American journal of Pharmtech research, 2014; 4(6): 492-502.
33. A Madhusudhan Reddy, Ayesha Siddika, P Surya Bhaskara Rao, P Manasa, J
Siddaiah, P Srinivasa Babu. Formulation and evaluation of sustained release
matrix tablets of Metformin HCl. Indian journal of research in pharmacy and
biotechnology, 2013; 1(2), 197-200.
34. Chandan Garg and Vikrant Saluja. Once-daily sustained-release matrix tablets of
Metformin HCl based on an enteric polymer and chitosan. Journal of
pharmaceutical educational research, 2013; 4(1), 92-97.
35. Kotta Kranthi Kumar, M. Narasimha Reddy, R.Naga Kishore. Formulation and
evaluation of bilayer matrix tablet of Pioglitazone HCl Metformin HCl USP 15mg
& 500mg. Asian journal of pharmaceutical and clinical research, 2013; 6(3), 155-
161.
36. Chinmaya Keshari Sahoo, A. Amulya Reddy, Vandana Kethavath and
PrashanthSurabi, Eshwar Mule. Designing of Sustained-Release Metformin HCl
129
Tablets for the Treatment of Type-II Diabetes Mellitus. Asian journal of chemical
and pharmaceutical research, 2013; 1(1): 42-46.
37. R Charulatha, et.al. Design and evaluation of acebrophylline sustained
release matrix tablets. Scholars Research Library, 2012; 4 (2): 530-535.
38. Mohd Abdul Hadi, et.al. Formulation and Evaluation of Sustained Release
Matrix Tablets of Montelukast Sodium. International Journal of Pharmacy,
2012; 2(3): 574-582.
39. Naga Raju Potnuri et al. Effect of binders, lubricants and fillers on drug
release from Diltiazem Hydrochloride Bi-Layered matrix tablets obtained
by direct compression and wet granulation technique. International
Journal of Pharmacy, 2012; 2(1): 117 – 128.
40. Kamlesh J et al. Formulation and evaluation of sustained release matrix
tablets of Metformin HCl using pH dependent and pH Independent
Methacrylate polymers. British Journal of Pharmaceutical Research,
2011; 1(2): 29 – 45.
41. Basavaraj K Nanjwade, et.al. Formulation and Extended-Release
Metformin HCl matrix tablet. Tropical Journal of Pharmacy, 2011; 10(4):
375 – 383.
42. Bangale G.S, et.al. Formulation and Evaluation of Natural Gum Based
Matrix Tablets for Oral Controlled Delivery of Nimodipine. Indian Journal
of Pharmaceutical Education and Research, 2011; 45(4): 252-268.
130
43. T Rajasekharan et al. Formulation and evaluation of Hydroxypropyl
methylcellulose based controlled release matrix tablets for Theophylline.
Indian Journal of Pharmaceutical Sciences, 2011; 50(4): 205 – 214.
44. Deepak Gupta et.al. Formulation and development of sustained release
matrix tablets containing Metformin HCl. Pharmacologyonline, 2011; 2:
879-885.
45. Himansu Bhusan Samal, et.al. Formulation and evaluation of sustained
release zidovudine matrix tablets. International Journal of Pharmaceutical
Sciences, 2011; 3 (2): 32-41.
46. Melike Uner et al. Design of Hydralazine Hydrochloride matrix tablets
based on various polymers and lipids. Indian Journal of Pharmaceutical
Education and Research Association of Pharmaceutical Teachers of
India, 2012; 46(1): 75 – 87.
47. Md Mofizur Rahman et al. Formulation and evaluation of Ranolazine
sustained release matrix tablets using Eudragit and HPMC. International
Journal of Pharmaceutical and Biomedical Research, 2011; 2(1): 7 – 12.
48. John Rojas et al. Formulation of a modified release Metformin HCl matrix
tablet: Influence of some hydrophilic polymers on release rate and In-Vitro
evaluation. Brazilian Journal of Pharmaceutical Sciences, 2011; 47(3):
483 – 493.
49. Dangi Amish A et al. Formulation and evaluation of extended release
Metformin HCl tablet: Effect of polymers and additives on drug release
131
mechanism. Asian Journal of Biochemical and Pharmaceutical Research,
2011; 1(2): 480 – 499.
50. Marget Chandira et al. Formulation and evaluation of extended release
tablets containing Metformin HCl. International Journal of Chemtech
Research, 2010; 2(2): 1320 – 1329.
51. G N K Ganesh et al. Preparation and evaluation of sustained release
matrix tablet of Diclofenac sodium using natural polymer. Journal of
Pharmaceutical Science and Research, 2010; 2(6): 360 – 368.
52. Shankar S J et al. Formulation and evaluation of controlled release matrix
tablet of an antimicrobial drug. International Journal of Pharma Research
and Development, 2010; 2(10): 8 – 14.
53. Ritu B Dixit et al. Formulation and characterisation of sustained release
matrix tablet of Metformin HCl. International Journal of Pharma Recent
Research, 2009; 1(1): 49 – 53.
54. Anroop B Nair et al. Controlled release matrix uncoated tablets of
Enalapril Maleate using HPMC alone. Journal of Basic and Clinical
Pharmacy, 2010; 1(2): 71 – 75.
55. Raghavendra Rao N G et al. Formulation and evaluation of matrix tablets
of Tramadol hydrochloride. International Journal of Pharmacy and
Pharmaceutical Sciences, 2009; 1(1): 61 – 70.
56. Panna Thapa et al. Formulation of once a day controlled release tablet of
Indomethacin based on HPMC-Mannitol. Kathmandu University Journal
of Sciences, Engineering and Technology, 2008; 1(5): 55 – 67.
132
57. Abdelkader H et al. Formulation of controlled release Baclofen matrix
tablet: Influence of some hydrophilic polymers on the release rate and in-
Vitro evaluation. American Association of Pharmaceutical Sciences,
2007; 8(4): 156 – 166.
58. Brunton L, Lazo J, Parker K Goodman and Gilman’s. The
pharmacological basis of therapeutic insulin, Oral Hypoglycaemic agents
and the pharmacology of the endocrine pancreas. McGraw-Hills: New
York, 2006; 11:132 – 156.
59. Gunter wolf. Dosage of Hyperglycaemic drugs in patients with renal
insufficiency: Diabetes and kidney disease. Wiley publishers, 2013; 230 -
238.
60. Dr Amy Lee and John E Morley. Metformin decreased food consumption
and induces weight loss in subjects with obesity with type II Non-Insulin-
Dependent Diabetes. Obesity Research, 1998; 47 – 53.
61. Ryan Jo Dowling et al. Understanding the benefits of Metformin use in
cancer treatment. Biomed Central Medicine, 2011; 9: 33.
62. Methocel Cellulose ethers Technical Handbook [Internet] 2002. Available
from: http://www.dow.com/dowwolff/en/pdf/192-01062.pdf.
63. Avicel RC/CL Microcrystalline cellulose and Sodium Carboxy methyl
cellulose: Material Safety Data Sheet [Internet] 2005 [updated 2008 Jan
31] Available from:
http://www.fmcbiopolymer.com/portals/pharm/content/docs/avicelrcclms
ds.pdf.
133
64. “Cellulose Acetate”. Encyclopaedia Britannica. Encyclopaedia Britannica
online. Encyclopaedia Britannica Inc., 2014. Web. 24 Dec.
2012 http://www.britannica.com/EBchecked/topic/101663/cellulose-
acetate.
65. Aerosil 200 Hydrophillic fumed silica. [Internet] 2011 Aug. Available from:
http://www.silmid.com/getattachment/e807b3bf-24eb-448d-a812-
e87cda6d0bd8/Aerosil-200.aspx.
66. Jaime Davidson and Harry Howlett. New prolonged-release Metformin
improves gastrointestinal tolerability. British journal of diabetes and
vascular disease, 2004; 4: 273-7.
67. Lieberman H A, Augsburger L L, Larry L A, Lachman L, Schwartz J B.
Granulation technology and tablet characterization. In: Pharmaceutical
Dosage forms: Tablets. 2nd ed: Taylor and Francis, 1990. Vol 2 p. 317 –
39.
68. N R Sheela et al. FTIR, FT Raman and UV-Visible Spectroscopic analysis
on Metformin HCl. Asian Journal of Chemistry, 2010; 22(7): 5049 – 5056.
69. Nilesh B Kulkarni, Pravin S Wakte and Jitendra B Naik. Metformin
Hydrochloride microparticles for oral controlled release: Effect of
formulation variables. International journal of pharmacy and
pharmaceutical sciences, 2013; 5(3): 135-144.
70. Indian Pharmacopoeia; In. 6 ed: Indian Pharmacopoeia Commission;
1996; Vol 2 p, Appendix 8.15, A-99.
134
71. Alfred martin. Physical pharmacy. Waverly International, 1995; 4th ed: p
332.
72. Subramaniyam CVS. Text Book of Physical Pharmaceutics, In. 2nd ed:
Vallabh Prakashan; 2000. p 258.
73. Subramaniyam CVS. Text Book of Physical Pharmaceutics; In. 2nd ed:
Vallabh Prakashan; 2000. p 202.
74. Leon Lachman, Liberman H A, Kanig J L. The theory and practice of
industrial pharmacy. Varghese publishing house Bombay, 1987; 3: 300.
75. Indian Pharmacopoeia; In. 6 ed: Indian Pharmacopoeia Commission;
1996; Vol 2 p, Appendix 8.15, A-99.
76. Leon Lachman, Liberman H A, Kanig J L. The theory and practice of
industrial pharmacy. Varghese publishing house, Bombay. 1987; 3: 297.
77. Leon Lachman, Liberman H A, Kanig J L. The theory and practice of
industrial pharmacy. Varghese publishing house, Bombay, 1987; 3: 249.
78. Guda Aditya et al. Design and evaluation of controlled release
Mucoadhesive buccal tablets of Lisinopril. International Journal of Current
Pharmaceutical Research, 2010; 2(4):24 – 27.
79. Indian Pharmacopoeia; In. 6 ed: Indian Pharmacopoeia Commission;
1996; Vol 2 p, Appendix 7.1, A-80.
80. Narender Sharma et al. Second derivative spectrophotometric method for
the estimation of Metformin HCl in bulk and in tablet dosage form.
International Journal of Pharmacy and Pharmaceutical Sciences, 2011;
3(4): 333 – 335.
135
81. Indian Pharmacopoeia; In. 6 ed: Indian Pharmacopoeia Commission;
1996; Vol 2 p, Appendix 7.3, A-82.
82. Subal Chandra Basak et al. Design and release characteristics of
sustained release tablet containing Metformin HCl. Brazilian Journal of
Pharmaceutical Sciences, 2008; 44(3); 477 - 483.
83. Suvakanta Dash et al. Kinetic modelling on drug release from controlled
drug delivery systems. Acta Polaniae Pharmaceutica – Drug research,
2010; 67(3): 217 – 223.
84. Gautam Singhvi, Mahaveer Singh. Review: In-vitro drug release
characterisation models. International Journal of Pharmaceutical Studies
and Research, 2011; 2(1): 77 – 84.
85. Omidian H, Park K, Introduction to hydrogels. In biomedical application of
hydrogels handbooks. Springer: New York, 2010; 1 – 16.
86. Lee P I and Peppas N A. Prediction of polymer dissolution in swelling of
controlled release systems. Journal of Controlled Release, 1987; 6: 207
– 215.
87. N A Peppas. Analysis of fickian and non fickian drug release from
polymers. Pharmacetica Acta Helvetiea, 1985; 60: 110 – 111.
88. Mukesh C Gohel et al. Assessment of similarity factor using different
weighing approaches. Dissolution Technologies, 2005; 22 – 27.
89. Food, Drug Administration HHS. International Conference on
Harmonisation. Guidance on Q1a Stability Testing of New Drug
136
Substances and Products. Availability, Notice. Fed. Regist. 2001.66(216):
56332 – 3.
90. Stability testing of active substances and pharmaceutical products. World
health organisation. 1211 Geneva, Switzerland, 2006, 1-33.
91. Arayne MS, et.al. Development and validation of RP-HPLC method for
analysis of Metformin. Pakistan Journal of Pharmaceutical Sciences,
2006; 19: 231-235.
92. Saadia Shahzad Alam et al. Alloxan Induced Diabetes in Rabbits.
Pakistan Journal of Pharmacology, 2005; 22 (2): 41 – 45.
93. Etuk E U. Animals models for studying diabetes mellitus. Agriculture and
Biological Journal of North America, 2010; 1 (2): 130 – 134.
94. Aulton M E. Pharmaceutics: The science of dosage form design. In. 2nd
ed. Churchill Livingstone, 2002. p. 159 – 61.
95. Donald L. Wise. Drug release from swelling-controlled system. Marcel
Dekker, 2005; 188 – 189.
96. Brahmankar DM, Sunil B Jaiswal. Biopharmaceutics and
Pharmacokinetics A Treatise. Controlled release medication. Vallabh
Prakashan, 2009; 2 ed: 400 – 405.
97. Brahmankar DM, Sunil B Jaiswal. Biopharmaceutics and
Pharmacokinetics A Treatise. Controlled release medication. Vallabh
Prakashan, 2009; 2 ed: 326 - 330.
137
98. Binghe Wang, Teruna Siahaan, Richard A Soltero. Physicochemical
Properties, Formulation and drug delivery: Drug delivery principles and
applications. Wiley Interscience, 2005: p 65.
99. Aulton M E. Pharmaceutics: The science of dosage form design. In. 2nd
ed: Churchill Livingstone, 2002. P. 159 - 61.
100. Liberman HA, Augsburger LL, Larry LA, Lachman L, Schwartz JB.
Granulation Technology and Tablet Characterisation. In: Pharmaceutical
Dosage Forms: Tablets. 2nd ed: Taylor and Francis; 1990. Vol 2 p 317 –
39.
101. Brahmankar DM, Sunil B Jaiswal. Biopharmaceutics and
Pharmacokinetics A Treatise. Controlled release medication. Vallabh
Prakashan, 2009; 2 ed: 331 – 332.
102. Choosing an experimental design. In: NIST/SEMATECH e-Handbook of
Statistical methods: NIST, 2012. Available from:
http://www.itl.nist.gov/div898/handbook/pri/section3/pri3.htm.
138
ANNEXURECHAPTER 9
139
9. ANNEXURE 9.1 Annexure 1: List of Materials
Sl.No List of Materials Source
1 Metformin HCl Caplin point laboratories Ltd
2 HPMC K4M Dr Reddys Laboratories
3 HPMC K15M Dr Reddys Laboratories
4 HPMC K100M Dr Reddys Laboratories
5 Carboxy methyl Cellulose Nice Chemicals, Kochi
6 Cellulose acetate Loba Chemicals, Mumbai
7 Aerosil 200 Loba Chemicals, Mumbai
8 Magnesium stearate Nice Chemicals, Kochi
9 Isopropyl alcohol Nice Chemicals, Kochi
10 Ethanol Nice Chemicals, Kochi
11 Alloxan monohydrate K M C , Coimbatore
12 Glipizide K M C , Coimbatore
13 Acetonitrile Loba Chemicals, Mumbai
14 Ortho phosphoric acid CDH Chemicals, New Delhi
15 Sodium citrate CDH Chemicals, New Delhi
16 Hydrochloric acid Nice Chemicals, Kochi
17 Disodium phosphate CDH Chemicals, New Delhi
18 Sodium hydroxide SD Fine Chemicals.
19 Disodium hydrogen phosphate SD Fine Chemicals.
20 Potassium chloride SD Fine Chemicals.
140
9.2 Annexure 2: List of Equipment
Sl. No List of equipment Manufacturer
1 Electronic precision balance Shimadzu, Analytical India Pvt Ltd
2 Tablet Punching machine Karnavati engineering, Gujarat.
3 Hot air oven Rotex India Pvt Ltd.
4 Pfizer type hardness tester Lyzer India
5 Roche Friabilator Lyzer India
6 UV Visible spectrophotometer Shimadzu, Analytical India Pvt Ltd
7 FT-IR spectrophotometer Shimadzu, Analytical India Pvt Ltd
8 HPLC Shimadzu, Analytical India Pvt Ltd
9 pH meter Lyzer India
10 Dissolution apparatus Electrolab India Pvt Ltd
11 Stability chamber Labline equipments Pvt Ltd
12 Centrifuge Lyzer India
141
9.3 Annexure 3: Published Journal Copy
142
143
144
9.4 Annexure 4: Animal ethical committee certificate
145