Biopharmaceutics PHT 414 Year 1436/37 - PSAU · Biopharmaceutics PHT 414 Year 1436/37 1st semester. Department of Pharmaceutics Biopharmaceutics PHT -414 ... Importance & applications

Prince Sattam bin Abdulaziz University

Pharmacy College

Pharmaceutics department

Biopharmaceutics

PHT 414

Year 1436/37

1st semester

Department of Pharmaceutics Biopharmaceutics PHT -414

Knowledge is power Page 1

Main subjects which will be covered in the labs.:

1. Introduction to Drug dissolution: definition, factors affecting it, USP official

tests.

2. How to construct a Calibration curve as a standard for measuring drug

concentration of dissolution samples.

3. Application of a standard dissolution test illustrating calculation as percent of

drug released versus time.

4. Application of a standard dissolution test illustrating calculation as

Cumulative percent of drug released versus time.

5. Study the Effect of pH of the medium on the rate of drug dissolution.

6. Study the Effect of formulation factor on the rate of drug dissolution.

7. Study the Effect of drug particle size on the rate of drug dissolution.

8. Study the Effect of viscosity of the dosage form on the rate of drug release.

9. What is Partition Theory? Calculate and determine the partition coefficient.

10. Evaluation of ocular drug delivery.



To attain these specific objectives the following rules must be

adhered to in the lab:

1. All students must wear clean, white lab coats while in the laboratory.

2. All students must follow the instructions of their teaching instructors.

3. All students must complete all laboratory assignments. If a lab is missed, the

reason for the absence must be discussed with the instructor prior to absence

and a makeup lab arranged. A substantial grade reduction will be given for

any assignment which is not completed.

4. Students who exhibit dishonest or unprofessional behavior in the lab may, at the

discretion of the instructor receive a failing grade for the laboratory portion of

the course.

5. Only a student’s best effort is to be submitted for grading.

6. Always bring with you: Scientific calculator and graph paper note book.

What are the responsibilities of each students:

1. The attendance of each lab is a must (1-4 p.m.) unless otherwise agreed with

instructor. 2. In the lab, students will work as groups. Each group will be graded on the

quality of their work and results. However, the report for each experiment

will be submitted by each student individually.

3. The report should be hand written and not done through a computer.

4. There will be a grade for each lab (2 marks /lab) including your attendance,

behavior, work and report.

5. There will be a final exam "Theoretical & Practical" for all labs involving all

subjects covered in labs.



Introduction to the Course Outline

Biopharmaceutics PHT-414

Lectures: One semester - Three hours per week

Laboratory: One semester - One (three hour) session per week

Grading

Attendance

Experimental Work

Behavior & performance

Report

0.25

0.5

0.25

1

Grade/lab 2

Grade (10 labs) 20

Final practical exam 10

Total 30

Department of Pharmaceutics Biopharmaceutics PHT-414


Coursework

LABORATORY EXPERIMENTS OUTLINE (414 PHT)

Week Topic Description

1

Introduction to drug

dissolution

Part 1

Theoretical background

2

Introduction to drug

dissolution

Part 2

Theoretical background

3 Experiment 1. Construction of a calibration curve

4

Experiment 2. Dissolution test – calculate percent drug

released

5 Experiment 3. Dissolution test – calculate cumulative percent

drug released

6 Experiment 4. Effect of pH on rate of drug dissolution

7 Experiment 5. Effect of drug particle size on rate of drug

dissolution

8 Experiment 6. Effect of formulation factor on rate of drug

dissolution

9

Experiment 7. Effect of viscosity on rate of drug dissolution

10 Experiment 8. How to determine the partition coefficient

11 Evaluation of non-oral drug

delivery

Ocular drug delivery (demonstration)

12 Final Exam

Practical and theoretical



Lab # 1 & 2

Introduction to dissolution test

LIST OF CONTENTS Introduction

Importance & applications

Factor affecting dissolution rate

1. Physicochemical Properties of Drug

2. Drug Product Formulation Factors

3. Processing Factors

4. Factors Relating Dissolution Apparatus

5. Factors Relating Dissolution Test Parameters

Various official dissolution tests

References

INTRODUCTION

Definition:- Dissolution rate may be defined as amount of drug substance that goes in the solution per

unit time under standard conditions of liquid/solid interface, temperature and solvent composition.

The processes involved in dissolution of solid dosage forms:



IMPORTANCE AND APPLICATIONS

1. PRODUCT DEVELOPMENT

Important tool during development of dosage form.

Aids in guiding the selection of prototype formulations and for determining optimum levels of

ingredients to achieve drug release profiles, particularly for extended release formulations.

2. QUALITY ASSURANCE

Used to assess the lot-to-lot performance characteristics of drug product and provide continued

assurance of product integrity/similarity.

3. PRODUCT STABILITY

Used to assess drug product quality with respect to stability and shelf-life. As product age,

physicochemical changes to the dosage form may alter dissolution characteristics of drug

product over time. For some products, polymorph transformations to more stable, and hence

less soluble crystalline forms may result in reduced dissolution rates.

4. COMPARABILITY ASSESSMENT

Also useful for assessing the impact of pre- or post- approval changes to drug product such as

changes to formulation or manufacturing process. Thus, in-vitro comparability assessment is

critical to ensure continued performance equivalency and product similarity.

5. WAIVERS OF IN-VIVO BIOEQUIVALENCE REQUIREMENTS

In-vitro dissolution testing or drug release testing may be used for seeking waiver of required

product to conduct in-vivo bioavailability or bioequivalence studies



FACTORS AFFECTING DISSOLUTION RATE

1. Physicochemical Properties of Drug

2. Drug Product Formulation Factors

3. Processing Factors

4. Factors Relating Dissolution Apparatus

5. Factors Relating Dissolution Test Parameters

1. PHYSICOCHEMICAL PROPERTIES OF DRUG

a. Solubility

- Aqueous solubility of drug is a major factor that determines its dissolution rate.

- Minimum aqueous solubility of 1% is required to avoid potential solubility limited absorption

problems.

- Initial dissolution rate is directly proportional to their respective solubility.

b. Salt formation - A common approach used to increase drug solubility and dissolution rate.

- Sodium salts dissolve faster than their corresponding insoluble acids e.g. sodium and potassium salts of

Penicillin G, sulfa drugs, phenytoin, etc.

- While in case of Phenobarbital dissolution of sodium salt was slower than that of weak acid.

- In case for weak base drug, strong acid salts, such as hydrochlorides and sulphates of weak bases such

as epinephrine, tetracycline are commonl used due to high solubility.

- However, free bases of chlortetracycline, methacycline were more soluble than corresponding

hydrochloride salt at gastric pH values, due to common ion suppression.

c. Particle size - There is a direct relationship between surface area of drug and its dissolution rate.

- Since, surface area increases with decrease in particle size, higher dissolution rates may be achieved

through reduction of particle size.

- Micronization of sparingly soluble drug to reduce particle size is by no means a guarantee of better

dissolution and bioavailability.

- Micronization of hydrophobic powders can lead to aggregation when powder is dispersed into

dissolution medium.

- So, increase in S.A. of drug does not always guarantee an equivalent increase in dissolution rate.

Rather, it is increase in the “effective” S.A., or area exposed to dissolution medium and not the

absolute S.A. that is directly proportional to dissolution rate.

- Hydrophobic drugs like phenacetin, aspirin shows decrease in dissolution rate as they tend to adsorb

air at the surface and inhibit their wettability. Problem eliminated by evacuating surface from adsorbed

air or by use of surfactants. So these drugs in-vivo exhibit excellent wetting due to presence of natural

surfactants such as bile salts.



d. Solid state characteristics - Solid phase characteristics of drug, such as

amorphicity, crystallinity, state of hydration and

polymorphic structures have significant

influence on dissolution rate.

- Anhydrous forms dissolve faster than hydrated

form because they are thermodynamically more

active than hydrates e.g. Ampicillin anhydrate

shows faster dissolution rate than trihydrate.

- Amorphous forms of drug tend to dissolve faster

than crystalline materials, e.g. Novobiocin

suspension, Griseofulvin.

- Metastable (high activation energy) polymorphic

forms have better dissolution than stable forms.

e. Co-precipitation

- Dissolution rate of sulfathiazole could be significantly increased by co-precipitating the drug with

povidone.

2. DRUG PRODUCT FORMULATION FACTORS - Dissolution rate of pure drug can be altered significantly when mixed with various adjuncts during

manufacturing process such as diluents, dyes, binders, granulating agents, disintegrants and lubricants.

a. Diluents

- Starch increases the dissolution rate of salicylic

acid. - Here starch particles form a layer on the outer surface

of hydrophobic drug particles resulting in imparting

hydrophilic character to granules & thus increase rate

of dissolution.

b. Disintegrants

- Starch is not only an excellent diluent but also superior disintegrant due to its hydrophilicity and

swelling property.

- Disintegration and dissolution rate of disintegrants with moderate swelling capacity depend to a large

extent on mixing time of drug/excipient pre-blend.



c. Binders and granulating agents

wettable drug.

disintegration /dissolution rate of tablet.

ethyl cellulose also retard the

drug dissolution.

Gelatin imparted hydrophilic character to hydrophobic

drug surface whereas PEG 6000 formed a poorly soluble

complex while CMC was converted to its less soluble acid

form at the low pH of gastric fluid.

d. Lubricants - Lubricants are hydrophobic in nature (metallic stearates) and prolong tablet disintegration time by

forming water repellant coat around individual granules decrease dissolution

- It should be added in small amount (1% or less) and should be tumbled or mixed gently for only very

short time.

- Prolonged mixing will retard the dissolution time.

e. Surfactants

- They enhance the dissolution rate of poorly soluble drug. This is due to lowering of interfacial

tension, increasing effective surface area, which in turn results in faster dissolution rate.

- E.g Non-ionic surfactant Polysorbate 80 increase dissolution rate of phenacetin granules.

f. Coating polymers - Tablets with methyl cellulose coating were found to exhibit lower dissolution profiles than those

uncoated.

- The differences are attributed to thermal gelation of MC at temp near 37º, which creates a gel layer

(barrier to dissolution process).



3. PROCESSING FACTORS

a. Method of granulation - Granulation process in general enhances dissolution rate of poorly soluble drug.

- A newer technology called as APOC “Agglomerative Phase of Comminution” was found to

produce mechanically stronger tablets with higher dissolution rates than those made by wet

granulation. A possible mechanism is increased internal surface area of granules produced by APOC

method.

b. Compression force - The compression process influence density, porosity, hardness, disintegration time & dissolution of

tablet.

First condition, higher compression force increase the density &

hardness of tablet, decrease porosity & hence penetrability of

solvent into the tablet retard the wettability by forming a firmer &

more effective sealing layer by the lubricant and in many case

tighter bonding between the particle so decrease dissolution rate of

tablet.

Second condition, higher compression force cause deformation,

crushing or fracture of drug particles into smaller ones or convert

spherical granules into disc shaped particles with a large increase in the

effective surface area so increase in dissolution rate.

Combination of both conditions can occur

c. Drug excipient interaction - These interactions occur during any unit operation such as mixing, milling, blending, drying, and/or

granulating result change in dissolution.

- The dissolution of prednisolone found to depend on the length of mixing time with Mg-stearate

d. Storage conditions - Dissolution rate is affected by storage condition of temperature and humidity which may result in

increase or decrease in the rate of drug dissolution.



4. FACTORS RELATING DISSOLUTION APPARATUS

a. Agitation

- In general relatively low agitation should be applied (to avoid turbulence and un reliable results)

I. BASKET METHOD- 100 rpm

II. PADDLE METHOD- 50-75 rpm

b. Stirring element alignment - The USP / NF XV states that the axis of the stirring element must not deviate more than 0.2 mm from

the axis of the dissolution vessel which defines centering of stirring shaft to within ±2 mm.

c. Sampling probe position & filter - Sampling probe can affect the hydrodynamic of the system & so that change in dissolution rate.

- For position of sampling, USP / NF states that sample should be removed at approximately half the

distance from the basket or paddle to the dissolution medium and not closer than 1 cm to the side of

the flask.

- Filter material must be saturated with the drug by repeated passage to avoid losses that might go

undetected during the test sampling.

- Accumulation of the particulate matter on the surface may cause significant error in the dissolution

testing.

5. FACTORS RELATING DISSOLUTION TEST PARAMETERS

a. Temperature - Drug solubility is temperature dependent, therefore careful temperature control during dissolution

process is extremely important.

- Generally, a temp of 37º ± 0.5 is maintained during dissolution determination of oral dosage forms

and suppositories. However, for topical preparations temp as low as 30º and 25º have been used

b. Dissolution medium

- It is very imp factor affecting dissolution and is itself affected by number of factors such as:

i. Effect of pH

For Weak acids, dissolution rate increases with increase in pH whereas for weak bases, increases

with decrease in pH

ii. Volume of dissolution medium and sink conditions generally 500, 900 or 1,000 ml.

- pH 1.2.

- pH 6.8 (not exceed pH 8.0).

-by-case like…. (Pepsin with SGF and pancreatin with

SIF

s poorly soluble, a relatively large amount of fluid should be used if complete dissolution is to

be expected.



should not exceed 10-15% of its max. Solubility in dissolution medium selected. For most of the drugs

about 1 L is more than sufficient to maintain sink conditions.

dissolution

medium that would be required to maintain the sink conditions. For these, different approaches have

been tried like….

1. Continuous flow method where fresh solvent is pumped continuously into dissolution flask at a fixed

flow rate while maintaining a constant volume.

2. Use of non-ionic surfactant in conc. above CMC.

3. Use of alcoholic solution (10-30%).

iii. Deaeration of dissolution medium air in distilled water could significantly lower its pH and consequently affect the dissolution

rate of drugs that are sensitive to pH changes, weak acids.

ect at

the surface of the dosage forms, thereby acting as a hydrophobic barrier between solvent and solid

surface. This inhibits wetting and reduction of S.A. and lower dissolution rate.



VARIOUS OFFICIAL DISSOLUTION TESTS

the dissolution tests provide the Compendial correlation to drug product performance.

1) Immediate release dosage forms: Powders, Granules / Beads, Capsules

2) Controlled release dosage forms: Powders, Granules / Beads, Capsules

3) Transdermal System

4) Implants

The dissolution apparatus has evolved gradually & considerably from a simple beaker type to a highly

versatile & fully automated instrument. Based on absence or presence of sink conditions, there are three

principal types of dissolution apparatus:

1. Closed-compartment- Basically a limited volume apparatus operating under non-sink conditions.

e.g. App-I & II.

2. Open compartment- One in which dosage form is contained in a column which is brought in

continuous contact with fresh, flowing dissolution medium (perfect sink condition)

3. Dialysis type system- Used for very poorly aqueous soluble drug for which maintenance of sink

conditions would otherwise require large volume of dissolution fluid.

OFFICIAL DOSSOLUTION MONOGRAPHS

According to I.P. & E.P. for solid dosage forms (tablets and capsules) dissolution apparatus used are:

1. Apparatus I – PADDLE APPARATUS

2. Apparatus II – BASKET APPARATUS

According to B.P. apparatus used are:

1. Apparatus I – BASKET APPARATUS

2. Apparatus II – PADDLE APPARATUS

3. Apparatus III – FLOW THROUGH CELL APPARATUS



According to USP 30 dissolution apparatus used are:

USP App DESCRIPTION ROT. SPEED DOSAGE FORM

I BASKET 50-120 rpm IR, DR, ER

II PADDLE 25-50 rpm IR, DR, ER

III RECIPROCATING

CYLINDER

6-35 dpm

IR, ER

IV FLOW-THRU CELL N/A ER, POORLY SOLUBLE API

V PADDLE OVER DISK 25-50 rpm TRANSDERMAL

VI CYLINDER N/A TRANSDERMAL

VII RECIPROCATING

HOLDER

30 rpm

ER

CONDITIONS (for all in general) 1. Temp. - 37±0.5oC

2. PH - ±0.05 unit in specified monograph

3. Capacity – 1000 ml

4. Distance between inside bottom of vessel and paddle/basket is maintained at 25±2 mm.

5. For enteric coated dosage form it is first dissolved in 0.1 N HCl & then in buffer of pH 6.8 to measure

drug release. (Limit – NMT 10% of drug should dissolve in the acid after 2hr.and about 75% of it should

dissolve in the buffer after 45 min.

1) Apparatus I- Basket Apparatus

40 mesh basket 20 mesh basket 10 mesh basket suppository basket

Unless otherwise specified in the individual monograph, use 40-mesh cloth.

Useful for: Capsules, Beads, Delayed release / Enteric Coated dosage forms

, Floating dosage forms



2) Apparatus-II - Paddle Apparatus. METHOD OF FIRST CHOICE.

A small, loose piece of no reactive material such as not more than a few turns of wire helix may be

attached to dosage units that would otherwise float.

Other validated sinker devices may be used.

PTFE coated paddle Solid PTFE coated paddle

Useful for: Tablets, Capsules, Beads, Delayed release, enteric coated dosage forms

Sinkers for floating dosage forms



References 1. Pharmaceutical dissolution testing by Umesh V. Banakar.

2. Remington 20th edition, 654.

3. Dissolution, Bioavailability & Bioequivalence by M. Abdou.

4. Biopharmaceutics & Pharmacokinetics by D.M.Bramankar, 20-29.

5. Generic Drug Product Development, vol-143 by Shargel.

6. Current concepts in pharmaceutical sciences & biopharmaceutics by James Swarbrick.

7. J. Pharm. Sci.,(73), 1186, 1984.

8. J. Pharm. Sci.,(65), 355, 1976.

9. J. Pharm. Sci.,(65), 572, 1976.

10. J. Pharm. Sci.,(59), 606, 1970.

11. J. Pharm. Sci.,(59), 49, 1970.

12. J. Pharm. Sci.,(52), 1139, 1963.

13. J. Pharm. Sci.,(52), 1050, 1963.

14. sAdvanced Drug Delivery Reviews,(46), 75-87, 2001.



Lab # 3

Construction of a calibration curve for paracetamol

Conditions:

o Material : Acetaminophen USP powder o Solvent : phosphate buffer pH 5.8

o Glass ware : 50 ml volumetric flasks : Micropipette

Procedure: 1. 10 mg drug was dissolved in 15 ml methanol and was shaken well. Then 85 ml water was

added to it to adjust the volume up to 100 ml (100 ppm).

2. Different sample volumes (X mL) were drawn from the stock solution and diluted with

phosphate buffer pH 5.8 to 50 ml volumetric flask to obtain concentrations of (2, 4, 6, 10, 20

ppm)

3. The diluted samples were then measured for acetaminophen concentration using UV

spectrophotometry at a wavelength of 243 nm.

Calculation:

Stock Solution

C1 (µg/ml) Q2 (ml) C2 (µg/ml)

Quantity taken

from stock soln.

Q1 (ml)

Absorbance

(243 nm)

100

50 2

50 4

50 6

50 10

50 20



- Draw the relationship between concentration (X-axis) and absorbance (Y-axis) and find the

equation and r2 (Calculated by the instructor via Excel program software).

- Use both the graph and the equation to calculate the concentration of paracetamol in a

sample of unknown concentration which showed absorbance of 0.45.



Lab # 4

DISSOLUTION TEST FOR PARACETAMOL TABLETS, (U.S.P. 1995),

Calculate the percent drug released as a function of time

Conditions: o Apparatus : I (Basket) o Medium : 900 ml of phosphate buffer pH 5.8

o Temp. : 37 ± 0.5 oC

o Speed : 100 rpm o Time : 30 min.

Procedure:

1. Place one tablet in the vessel, and then start the apparatus at the above conditions.

2. At specified time intervals (5, 10, 15, 20, 25, 30 min) withdraw 1 ml sample and place the

sample in a test tube. Replace the withdrawn sample with 1 ml fresh phosphate buffer kept

at 37 ± 0.5 o

C.

3. Dilute 1 ml of the collected sample to 25 ml (dilution factor = 25) with fresh phosphate

buffer (in a volumetric flask), mix well.

4. Read the absorbance for the diluted samples at 243 nm against a blank of phosphate

buffer.

5. Calculate the concentration of paracetamol released (from the Linear Regression equation

of the line obtained by plotting the standard calibration curve) and express this

concentration as a percentage of the labeled amount.

6. Plot the dissolution curve of paracetamol (% released vs. time).

7. From the dissolution curve, determine the time required for 80% of the labeled

USP stated that: the tablet should release not less than 80% of its content within 30 minutes

and not less than 90% of its content within 45 minutes. (For immediate release tablets)



Results of the dissolution --------------------------:

Time

(min)

Abs.

at 243 nm

Dilution factor =

( total vol / vol

taken from the

sample)

Conc. =[(abs-intercept)/slope]x

dil factor x 900/1000

(mg/900ml)

% released =

(conc./original

strength) x

100 5

10

15

20

25

30

• Plot the Time versus % release on graph paper • Determine the t80% of the drug??



Lab # 5

DISSOLUTION TEST FOR PARACETAMOL TABLETS, (U.S.P.

1995), Calculate the Cumulative percent drug released as a function

of time Conditions:

o Apparatus : I (Basket) o Medium : 900 ml of phosphate buffer pH 5.8

o Temp. : 37 ± 0.5 oC


Procedure:

1. Place one tablet in the vessel, and then start the apparatus at the above

conditions.

2. At specified time intervals (5, 10, 15, 20, 25, 30 min) withdraw 1 ml sample and

place the sample in a test tube. Replace the withdrawn sample with 1 ml fresh

phosphate buffer kept at 37 ± 0.5 o

C.

3. Dilute 1 ml of the collected sample to 25 ml (dilution factor = 25) with fresh

phosphate buffer (in a volumetric flask), mix well.

4. Read the absorbance for the diluted samples at 243 nm against a blank of

phosphate buffer.

5. Calculate the concentration of paracetamol released (from the Linear Regression

equation of the line obtained by plotting the standard calibration curve) and

express this conc. as a cumulative percentage of the labeled amount.

6. Plot the dissolution curve of paracetamol (Cumulative % released vs. time).


USP stated that: the tablet should release not less than 80% of its content within 30

minutes and not less than 90% of its content within 45 minutes. (For immediate

release tablets)



Results of the dissolution --------------------------:

Time

(min)

Abs.

at 243 nm

Dilution factor =

( total vol / vol

taken from the

sample)

Conc. =[(abs-

intercept)/slop

e] x dil factor

/1000

(mg/ml)

Cumulative Conc. =

[Conc. x 900] +

Conc. in 1ml of

previous samples

Cumulative %

released =

(Cumulative

conc./original

strength) x

100

5

10

15

20

25

30

45

• Plot the Time versus cumulative % release on graph paper • Determine the t50% of the drug??



Lab # 6

Effect of pH on the Drug Dissolution

DISSOLUTION TEST FOR DICLOFENAC POTASSIUM

TABLETS (immediate release tablets)

Conditions: o Apparatus : I (basket) o Medium : 900 ml of 0.1 M HCl pH 1.2 o Medium : 900 ml of 0.05 M phosphate buffer pH 4.5 o Medium : 900 ml of 0.05 M phosphate buffer pH 7.4

o Temp. : 37 ± 0.5 oC


Procedure: 1. Place one tablet in the basket, immerse in the vessel, and then start the

apparatus at the above conditions.

2. At specified time intervals (5, 10, 15, 20, 25, and 30 min) withdraw 5 ml

sample from the dissolution medium and place the sample in a test tube. 3. Replace the withdrawn sample with 5 ml fresh phosphate buffer kept at

37±0.5oC.

4. Read the absorbance for the samples at 276 nm against a blank of 0.1 M

HCl solution pH 1.2 or a blank of phosphate buffer.

5. Calculate the concentration of diclofenac potassium released (dividing by 0.031

as the value of the correction constant), and express this conc. as a percentage

of the labeled amount. 6. Plot the dissolution curve of diclofenac potassium (% released vs. time).


amount of the drug to be released i.e., t 80%.



Results of the dissolution of Diclefenac potassium tablets (25 mg) at pH 1.2



• Plot the Time versus % release on graph paper and comment on the

effect of the pH on the drug released rate??

Time

(min)

Abs. at

276

nm

(mg/900ml)

5

10

15

20

25

30

Time

(min)

Abs. at

276

nm

(mg/900ml)

5

10

15

20

25

30

Time

(min)

Abs. at

276

nm

(mg/900ml)

5

10

15

20

25

30



Lab # 7

Effect of the Particle Size on the Drug Dissolution

DISSOLUTION TEST FOR ASIPIRIN GRANULES (Different size)

Conditions: o Apparatus : I (Basket)

o Medium : 900 ml of phosphate buffer pH 5.5 in water ((official)

o Temp. : 37 ± 0.5 oC

o Speed : 100 rpm. o Time : 30 min.

Procedure: 1. Place 500 mg granules (>800 g, 300-800 g, <300 g) in the vessel, and

then start at the above conditions.

2. At specified time intervals (5, 10, 15, 20, 25, 30 min) withdraw 5 ml sample and place the sample in a test tube. Replace the withdrawn sample with 5 ml

fresh phosphate buffer kept at 37 ± 0.5 o

C. 3. Dilute 5 ml of the collected sample to 25 ml (dilution factor = 5) with fresh

phosphate buffer (in a volumetric flask), mix well.

4. Read the absorbance for the diluted samples at 272 nm against a blank of

phosphate buffer.

5. Calculate the concentration of drug released (multiply by 0.196 as the value of the correction constant), and express this conc. as a percentage of the labeled

amount.

6. Plot the dissolution curve of acetylsalicylic acid (% released vs. time).


amount of the drug to be released i.e., t 80%.



Results of the dissolution of Aspirin granules >800 g:

Time

(min)

Abs.

at 272 nm

Dilution factor =

( total vol / vol

taken from the

sample)

Conc. =Abs. x dil factor x K*

x 900 /1000

(mg/900ml)

% released =

(conc./original

strength) x 100

5

10

15

20

25

30 K* = 0.196

Results of the dissolution of Aspirin granules 300-800 g:

Time

(min)

Abs.

at 272 nm

Dilution factor =

( total vol / vol

taken from the

sample)

Conc. =Abs. x dil factor x K

x 900 /1000

(mg/900ml)

% released =

(conc./original

strength) x 100

5

10

15

20

25

30

Results of the dissolution of Aspirin granules <300 g:

Time

(min)

Abs.

at 272 nm

Dilution factor =

( total vol / vol

taken from the

sample)

Conc. =Abs. x dil factor x K

x 900 /1000

(mg/900ml)

% released =

(conc./original

strength) x 100

5

10

15

20

25

30

• Plot the Time versus % release on graph paper and comment on the effect of

the particle size on the drug released rate?



Lab # 8

Effect of the Formulation Factor on the Drug Dissolution

DISSOLUTION TEST FOR DICLOFENAC TABLETS, WITH

DIFFERENT FORMULATIONS (IMMEDIATE, ENTERIC,

SUSTAINED) Conditions:

o Apparatus : I (Basket) o Medium : 900 ml of phosphate buffer pH 6.8

o Temp. : 37 ± 0.5 oC


Procedure: 1. Place one tablet from each formulation in the vessel, and then start the

apparatus at the above conditions.

2. At specified time intervals (5, 10, 15, 20, 25 and 30 min) withdraw 5 ml sample

through a pipette, and place the sample in a test tube. Replace the withdrawn

sample with 5 mlfresh phosphate buffer kept at 37 ± 0.5 o

C.

3. Read the absorbance for the samples at 276 nm against a blank of

phosphate buffer.

4. Calculate the concentration of diclofenac released and express this conc. as a

percentage of the labeled amount.

5. Plot the dissolution curve of diclofenac (% released Vs time). 6. From the dissolution curve, determine the time required for 80% of the labeled



Results of the dissolution of Immediate release tablets:

Results of the dissolution of Enteric coated tablets:

Results of the dissolution of Sustained release tablets:

• Plot the Time versus % release on graph paper and comment on the

effect of the Different Formulation factor on the drug released rate? • Determine the t80% of the drug?

Time

(min)

Abs. at

276

nm

(mg/900ml)

5

10

15

20

25

30

Time

(min)

Abs. at

276

nm

(mg/900ml)

5

10

15

20

25

30

Time

(min)

Abs. at

276

nm

(mg/900ml)

5

10

15

20

25

30



Lab # 9 Effect of the Viscosity on the Drug Dissolution

Conditions: o Apparatus : Beaker1 Ltr. o Medium : 900 ml of phosphate buffer pH 5.8 in water

o Temp. : 37 ± 0.5 oC

o Stirring : Stirring with magnetic stirrer at constant mild speed. o Time : 30 min.

Procedure: 1- Place 5 g of 10% paracetamol solution (2% HPMC 100cps or 2% HPMC

4000 cps or 2% HPMC 100000 cps) in a cellulose bags of constant surface area

and then put them in the beaker and then start shaking as mentioned. 2- At specified time intervals (5, 10, 15, 20, 25 and 30 min) withdraw 1 ml

sample place the sample in a test tube. Replace the withdrawn sample with 1

ml fresh phosphate buffer kept at 37 ± 0.5 o

C. Dilute 1 ml to 25 ml.

3- Read the absorbance for the samples at 243 nm against a blank of phosphate buffer.

4- Calculate the concentration of paracetamol released and express this conc. as a

percentage of the labeled amount.

5- Plot the dissolution curve of paracetamol (% released vs. time).



Results of the dissolution of 2% HPMC 100 solution:

Time

(min)

Abs.

at 243 nm

Dilution factor =

( total vol / vol

taken from the

sample)

Conc. =[(Abs-intercept)/slope]x


(mg/900ml)

% released =

(conc./original

strength) x 100

5

10

15

20

25

30


Time

(min)

Abs.

at 243 nm

Dilution factor =

( total vol / vol

taken from the

sample)



(mg/900ml)

% released =

(conc./original

strength) x 100

5

10

15

20

25

30


Time

(min)

Abs.

at 243 nm

Dilution factor =

( total vol / vol

taken from the

sample)



(mg/900ml)

% released =

(conc./original

strength) x 100

5

10

15

20

25

30

• Plot the Time versus % release on graph paper and comment on the effect of the polymer viscosity on the drug released rate?



Lab # 10

Partition Coefficient

Aim

Determination of partition coefficient (k) of caffeine between benzene and

water

Introduction

If a solute is added to two immiscible solvents, A and B. in contact with each other,

the solute distributes itself between the two and equilibrium is set up between the

solute molecules in solvent A and the solute molecules in solvent B. The ratio of

the concentration of the solute in the two solvents is

where K is known as the partition coefficient or distribution coefficient.

Chemicals

Caffeine solution: (20 µg /ml) (MW 149.1)

Volume of solvent: 20 ml.

Shaking time: 10 min.

λ max = 274 nm.

Apparatus

100 ml separating funnel, cylinder, stoppered bottle.

Procedure

1- Measure accurate 20 ml of caffeine solution (20µ /ml) in stoppered bottle, added 20 ml of benzene. 2- Shake vigorously for 10 min and then set aside for 5 min. 3- Transfer to separating funnel, separate the aqueous phase, and filtrate if necessary. 4- Measure the absorbance of aqueous phase at 274 nm.



5- Calculate the conc. of caffeine (µg /ml). Calculation: Cw = Conc. of caffeine remaining in aqueous phase (after shaking) = Abs. x B (19.5) Where B is a constant Corg. = Conc. of caffeine remaining in organic phase = 20 µg/ml - Cw. 6- Calculate the partition coefficient K as follows

Comment on your results



Lab # 11

Ophthalmic preparations:

Definition: They are specialized dosage forms designed to be instilled onto the

external surface of the eye (topical), administered inside (intraocular) or adjacent

(periocular) to the eye or used in conjunction with an ophthalmic device.

The most commonly employed ophthalmic dosage forms are solutions,

suspensions, and ointments.

The newest dosage forms for ophthalmic drug delivery are: gels, gel-forming

solutions, ocular inserts, intravitreal injections and implants.

Drugs used in the eye:

Miotics e.g. pilocarpine Hcl

Mydriatics e.g. atropine

Cycloplegics e.g. atropine

Anti-inflammatories e.g. corticosteroids

Anti-infectives (antibiotics, antivirals and antibacterials)

Anti-glucoma drugs e.g. pilocarpine Hcl

Surgical adjuncts e.g. irrigating solutions

Diagnostic drugs e.g. sodiumfluorescein

Anesthetics e.g. tetracaine

Ideal ophthalmic delivery system:

Following characteristics are required to optimize ocular drug delivery system:

Good corneal penetration.

Prolong contact time with corneal tissue.



Simplicity of instillation for the patient.

Non irritative and comfortable form

Appropriate rheological properties

CLASSIFICATION OF OCULAR DRUG DELIVERY SYSTEMS:

1. Liquid

a. Topical eye drops (Solutions, suspensions, powder for reconstitiution)

b. Sol to gel systems

2. Semi solid (ointments, gel)

3. Solid (ocular inserts)

4. Intra-ocular dosage forms (injections. Irrigation solutions, implants)

Inactive Ingredients in Topical Drops:

They are added to perform the following functions:

1. For tonicity and tonicity adjusting agents:

- They should have an osmotic pressure as that of tear fluids (equal to 0.9%

NaCl)

- The eye can tolerate isotonicity range of 0.6-2% NaCl.

- Examples: NaCl, dextrose, glycerin, propylene glycol & mannitol.

2. For pH adjustment and buffers

pH adjustment (pH 7.4, normal physiological pH of tear fluid) is very important as pH

affects:

- to render the formulation more stable.

- The comfort, safety and activity of the product.

- Eye irritation increase in tear fluid secretion

- Rapid loss of medication.

- to enhance aqueous solubility of the drug.

- to enhance the drug bioavailability

- to maximize preservative efficacy

N.B. The concentration of the buffer should be as low as possible.



Examples: Isotonic phosphate vehicle pH ranges from 5.8-9

3. Stabilizers and anti-oxidants

- They are added to decrease rate of decomposition of active ingredients

- Examples: Sodium bisulphite, ascorbic acid, sodium thiosulfate.

4. Surfactants

- The order of surfactant toxicity is: anionic> cationic> non –ionic.

- Non-ionic surfactants are used to aid dispersing of steroids in suspensions and

to improve solution clarity

- Examples: tween 20 or 80

5. Viscosity imparting agents

- Examples: Polyvinyl alcohol, HPMC, methyl cellulose.

- They are added to increase viscosity of ophthalmic solutions.

- They increase ocular contact time, increase the muco-adhesiveness and

decrease the drainage rate.

- They also have a lubricating effect.

6. Vehicles:

- Mainly purified water USP.

Oils for drugs sensitive to moisture but should be of high purity and protected against

rancidity e.g. vegetable oils like olive oil, sesame oil and castor oil.

******** Best Wishes ********

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Biopharmaceutics PHT 414 Year 1436/37 - PSAU · Biopharmaceutics PHT 414 Year 1436/37 1st semester. Department of Pharmaceutics Biopharmaceutics PHT -414 ... Importance & applications