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174
8. Formulation and evaluation of mucoadhesive hydrogels of
Famotidine
The mucoadhesive hydrogels of Famotidine were prepared by
physical cross linking ionotropic gelation method, which is the method
most widely, used by a good number of researchers for the
preparation of alginate beads and hydrogels.
8.1 Construction of calibration curve
An accurately weighed 100 mg of Famotidine was dissolved in
pH 1.2 Hcl as per I.P178 and make up the volume up to 100 ml in a
volumetric flask, (Stock Solution: I, 1000 µg/ml). From this 10 ml of
solution was pipetted out and make up the volume up to 100 ml
(Stock Solution: II, 50 µg/ml). Then the aliquots were prepared, whose
concentration ranging from 2 to 20 µg/ml and the absorbance were
measured at 265 nm by using by using UV spectrophotometer,
Schimadzu-1200, against the reagent blank.
Table 8.1: Calibration curve data of Famotidine at pH 1.2
Concentration in µg/ml Absorbance at 265 nm0 02 0.0744 0.1476 0.2068 0.26810 0.34512 0.41814 0.48816 0.55118 0.62720 0.742
175
Fig: 8.1. Calibration curve of Famotidine
8.2 Formulation of mucoadhesive hydrogels
8.2.1 Formulation of placebo hydrogel beads
The Hydrogels were prepared by the method of physical
crosslinking (orifice ionotropic gelation technique). An accurately
weighed quantity of sodium alginate, HPMC - K100, SCMC and
carbopol were dissolved in required quantity of distilled water and this
solution is being homogenised at 500 rpm for 30 min. This solution
was sonicated for 30 min to remove air bubbles thus the solution was
dropped into 2 % cacl2 solution (crosslinking agent) using 21G syringe
and the formed hydrogels were cured for 30 min. These hydrogels
176
were washed with distilled water and dried at room temperature for 12
hours179.
8.2.2 Formulation of drug encapsulated hydrogel beads
Beads containing Famotidine were prepared by employing
sodium alginate in combination with HPMC-K100, SCMC, and
carbopol. An orifice ionic gelation process was used to prepare large
sized alginate beads. Sodium alginate and polymers were dissolved in
distilled water to form a homogeneous polymer solution; Famotidine
was added to the polymer solution and mixed thoroughly to form a
smooth viscous dispersion made upto 100 ml. The resulting
dispersion was then injected as a thin stream in to a 2 % w/v calcium
chloride solution was then added slowly while stirring for ionic
gelation reaction. Stirring was continued for 15 min to complete the
curing reaction and to produce spherical beads. Mixture was then
centrifuged and the product thus separated was washed repeatedly
with water and dried at room temperature for 12 hours. The prepared
beads were stored in a dessicator for further studies.
177
Table 8.2: Composition of mucoadhesive hydrogels of Famotidine
Formulation
Code
Drug
in g
Polymers in g
Sodium
alginateHPMC -K100
SCMC Carbopol
H1 0.5 1.0 2.0 - -
H2 0.5 1.0 - 2.0 -
H3 0.5 1.0 - - 2.0
H4 0.5 1.0 1.0 1.0 -
H5 0.5 1.0 1.0 - 1.0
H6 0.5 1.0 - 1.0 1.0
H7 0.5 1.0 1.0 0.5 0.5
H8 0.5 1.0 0.5 0.5 1.0
H9 0.5 1.0 0.5 1.0 0.5
H10 0.5 1.0 1.5 0.5 -
H11 0.5 1.0 - 1.5 0.5
H12 0.5 1.0 0.5 - 1.5
H13 0.5 1.0 1.5 - 0.5
H14 0.5 1.0 0.5 1.5 -
H15 0.5 1.0 - 0.5 1.5
2% W/V solution of calcium chloride is used as crosslinking agent.
178
Fig: 8.2 (a & b). Formulation H1 before and after drying
Fig: 8.3 (a & b). Formulation H9 before and after drying
Fig: 8.4 (a & b). Formulation H13 before and after drying
179
8.3 Evaluation of Famotidine hydrogels
8.3.1 Evaluation of micromeritic properties
Angle of repose
Angle of repose has been used as an indirect method of
quantifying powder flow ability, because of their relationship with
interparticle cohesion. A static heap of powder will begin to slide when
the angle of inclination is large enough to overcome frictional forces.
This sliding will stop when the angle of inclination is below to that of
the required to overcome adhesion/cohesion, i.e. sliding occurs until
the gravitational forces balance the inter-particle forces. This balance
of forces causes the powder poured from a container onto a horizontal
surface to form conical mount or heap. The sides of the heap formed
in this way make an angle with the horizontal which is called the
angle of repose represented by θ.
Where θ = Angle of repose
h = height of heap
r =horizontal surface radius of heap.
Bulk density
An accurately weighed quantity of hydrogel beads were poured
into graduated cylinder. Then the volume was measured directly from
the graduation marks on the cylinder as ml. The volume measure was
called as the bulk volume and the bulk density is calculated by
following formula
180
Tapped density
Tapped density refers to the bulk density of the powder after a
specified compaction process, usually involving vibration of the
container. After measuring the bulk volume the same measuring
cylinder was set into tap density apparatus. The tapped density is
calculated by the following formula.
Carr’s Index
It is one of the most important parameter to characteristic the
nature of powders and granules. It can be calculated from the
following equation.
Hausner’s ratio
Hausner’s ratio is an important character to determine the flow
property of powder and granules. This can be calculation by the
following formula
181
Table 8.3: Micrometric properties of formulations H1 – H15
Formulationcode
Angle ofrepose(θ) ± SD
Bulkdensity(g/cc) ±SD
Tappeddensity(g/cc) ±SD
Carr’sindex(%) ± SD
Hausner’sratio± SD
H1 28.15 ±0.015
0.797 ±0.010
0.904 ±0.026
11.83 ±0.115
1.131 ±0.015
H2 30.65 ±0.017
0.811 ±0.005
0.862 ±0.005
05.91 ±0.152
1.062 ±0.010
H3 20.72 ±0.011
0.524 ±0.011
0.561 ±0.011
06.65 ±0.057
1.070 ±0.005
H4 30.04 ±0.022
0.728 ±0.015
0.827 ±0.010
11.97 ±0.115
1.135 ±0.011
H5 20.15 ±0.015
0.832 ±0.015
0.896 ±0.010
07.14 ±0.111
1.076 ±0.005
H6 21.49 ±0.005
0.787 ±0.015
0.840 ±0.011
06.30 ±0.010
1.067 ±0.005
H7 27.73 ±0.011
0.717 ±0.005
0.743 ±0.005
03.59 ±0.010
1.036 ±0.011
H8 26.96 ±0.026
0.840 ±0.011
0.896 ±0.026
06.25 ±0.012
1.066 ±0.026
H9 26.53 ±0.05
0.678 ±0.026
0.710 ±0.015
05.21 ±0.005
1.047 ±0.023
H10 27.82 ±0.015
0.698 ±0.018
0.745 ±0.005
06.30 ±0.015
1.067 ±0.016
H11 24.86 ±0.010
0.785 ±0.015
0.837 ±0.012
06.21 ±0.012
1.071 ±0.012
H12 27.93 ±0.011
0.446 ±0.012
0.464 ±0.011
04.27 ±0.015
1.040 ±0.005
H13 24.98 ±0.026
0.655 ±0.005
0.694 ±0.005
05.62 ±0.010
1.059 ±0.011
H14 28.75 ±0.011
0.854 ±0.010
0.920 ±0.015
07.17 ±0.026
1.077 ±0.012
H15 29.38 ±0.015
0.775 ±0.011
0.821 ±0.011
05.60 ±0.011
1.061 ±0.011
8.3.2 Evaluation of Equilibrium Swelling Ratio (ESR)
Swelling of hydrogels was carried out in triplicate by gravimetric
method. Known weight of hydrogels for were taken and immersed
excess of 1.2 Hcl buffer for different time intervals at 37ºc and then
hydrogels were removed, wiped with tissue paper to remove excess of
182
solvent and weighed immediately. The difference in weight has given
the amount of water up taken by hydrogels after definite time
intervals180.
Where, wt = weight of hydrogels at time.
wo = initial weight of hydrogels.
Table 8.4: Swelling ratio data for all formulations
Formulationcode
Time in h1 2 3 4 5 6
H1 1.2±0.05
2.6±0.1
4.5±0.1
5.4±0.15
7.2±0.05
7.6±0.05
H2 2.2±0.05
3.6±0.05
4.4±0.05
6.4±0.05
7.3±0.05
8.3±0.05
H3 2.7±0.11
4.3±0.05
6.2±0.11
7.5±0.1
10.7±0.05
11.2±0.05
H4 0.5±0.15
2.6±0.15
3.6±0.05
4.3±0.05
6.6±0.05
7.8±0.05
H5 1.3±0.1
3.4±0.15
4.7±0.05
5.4±0.05
7.3±0.11
9.3±0.11
H6 1.7±0.1
4.6±0.1
6.5±0.15
7.5±0.05
9.6±0.05
10.5±0.05
H7 1.0±0.1
2.6±0.1
5.3±0.11
9.4±0.05
9.6±0.05
10.6±0.05
H8 1.6±0.1
3.3±0.15
7.4±0.05
8.2±0.05
10.6±0.05
10.6±0.05
H9 2.5±0.05
4.8±0.15
6.9±0.05
8.9±0.05
9.6±0.05
10.6±0.05
H10 1.3±0.06
2.7±0.01
4.4±0.04
5.6±0.25
7.5±0.05
8.2±0.05
H11 2.3±0.05
3.4±0.05
5.1±0.05
7.2±0.05
7.8±0.05
8.5±0.05
H12 3.7±0.01
5.3±0.04
7.8±0.15
8.5±0.06
9.±0.07
10.9±0.08
H13 2.5±0.1
4.7±0.05
7.5±0.05
9.5±0.05
12.6±0.05
14.6±0.05
H14 2.3±0.11
4.4±0.15
6.7±0.05
8.4±0.05
9.3±0.11
10.3±0.11
H15 3.7±0.11
5.6±0.12
7.5±0.15
9.5±0.05
11.6±0.05
13.6±0.05
183
Fig: 8.5 Swelling ratio of Famotidine mucoadhesive hydrogels
8.3.3 Water uptake studies
Known weight of hydrogels for were taken and immersed in
excess of distilled water at 37ºc. Then the hydrogels were removed at
particular time intervals, wiped with tissue paper to remove excess of
solvent and weighed immediately. The difference in weight has given
the amount of water uptake by hydrogels for definite period of time181.
Where, WS = weight of swollen hydrogels.
WD = weight of dried hydrogels.
184
Table 8.5: Water uptake data for all formulations
Formulationcode
Time in h1 2 3 4 5 6
H1 68.72±0.16
81.06±0.15
85.18±0.05
89.30±0.02
93.41±0.11
97.53±0.15
H2 65.82±0.05
78.95±0.02
82.35±0.02
84.18±0.08
89.32±0.13
92.64±0.16
H3 63.83±0.02
75.32±0.01
79.65±0.15
82.14±0.15
87.64±0.13
90.85±0.03
H4 57.46±0.15
70.88±0.16
73.66±0.16
75.12±0.12
82.48±0.14
84.98±0.17
H5 55.48±0.16
68.46±0.05
71.64±0.14
73.19±0.12
80.68±0.08
83.36±0.03
H6 54.45±0.02
66.72±0.01
70.84±0.14
72.18±0.15
78.89±0.11
82.66±0.05
H7 61.88±0.16
73.62±0.05
76.46±0.04
80.60±0.06
85.18±0.18
88.26±0.01
H8 60.44±0.05
72.48±0.12
75.64±0.12
78.81±0.14
84.46±0.02
87.16±0.16
H9 58.64±0.25
70.24±0.12
73.18±0.15
76.64±0.04
82.24±0.06
85.58±0.05
H10 66.32±0.25
79.65±0.11
83.12±0.13
85.60±0.16
90.85±0.03
93.41±0.15
H11 56.56±0.16
69.84±0.02
72.68±0.03
74.16±0.12
81.84±0.16
84.43±0.16
H12 52.54±0.05
64.63±0.16
68.82±0.15
70.68±0.05
76.46±0.16
80.84±0.13
H13 64.32±0.25
77.41±0.25
84.82±0.05
87.64±0.16
91.42±0.14
99.89±0.19
H14 62.56±0.25
74.88±0.015
78.92±0.16
81.65±0.06
86.42±0.03
89.30±0.07
H15 50.48±0.04
62.26±0.16
70.48±0.16
72.61±0.01
80.42±0.02
83.34±0.04
185
Fig: 8.6 Water uptake of Famotidine mucoadhesive hydrogels
8.3.4 Evaluation of gel fraction
To extract the insoluble parts of hydrogels (i.e., the gelled part),
the prepared hydrogels were soaked in water for 48 h. Then they were
taken out and washed with hot water to remove soluble part, dried
and weighed. Gel fraction was determined from equation given
below182
Where, wo = weight of dried hydrogel after crosslinking.
we = weight of Sample after extraction of soluble parts.
186
8.3.5 Morphological evaluation
Size analysis by optical microscopy
After drying at 37ºC for 48 hours, the mean diameter of the
dried beads was measured by using an optical micrometer fitted with
a calibrated eye piece. The mean of 100 beads was noted as particle
size. The sizes of both dried and wet beads were measured. All reading
is average of three trials183.
Surface morphological studies by SEM analysis
The surface morphological studies and shape of the dried
hydrogels were examined by using scanning electron microscopy.
Fig: 8.7 (a & b) SEM Photographs of Formulation F1
187
Fig: 8.8 (a & b) SEM Photographs of Formulation F6
Fig: 8.9 (a & b) SEM Photographs of Formulation F13
Fig: 8.10 (a & b) SEM Photographs of Formulation F15
188
8.3.6 Physicochemical evaluation
Percentage yield
Percentage yield was calculated by using equation given below
Drug content
100 mg equivalent weight of Famotidine hydrogels were
triturated using mortar and pestle. Then the triturated hydrogels were
placed in volumetric flask and the volume was made upto 100 ml with
pH 7.4 phosphate buffer solution and kept aside for 24 h. After
specified time intervals these hydrogels were filtered and make
necessary dilutions, then the absorbance were measured at 265 nm
spectrophotometrically184.
Drug entrapment efficiency
The 100 mg equivalent hydrogels were soaked and digested in
100 ml of pH 1.2 Hcl for 24 h and then the solution was filtered. The
absorbance was analysed spectrophotometrically at 265 nm after a
necessary dilutions. At least three determinations were carried out for
each formulation for the determination of drug entrapment185.
189
Table 8.6: Physicochemical evaluation of Famotidine hydrogels
Formulation code
%Yield
Drugcontent
(mg)
Drugentrapmentefficiency
Gelfraction
Size analysisDriedbeads
Wetbeads
H1 95.8±0.11
96.9±0.15
95.4±0.05
95.2±0.11
1.83±0.51
2.93±0.47
H2 98.4±0.15
96.2±0.12
93.2±0.15
92.6± 0.32
1.48±0.02
2.66±0.32
H3 97.3±0.16
94.4±0.11
92.4±0.11
91.8±0.41
1.65±0.04
2.51±0.21
H4 92.6±0.12
85.3±0.25
86.2±0.16
84.8±0.21
1.68±0.22
2.67±0.41
H5 93.2±0.25
86.8±0.05
86.8±0.08
85.6±0.15
1.52±0.12
2.58±0.22
H6 91.7±0.11
82.4±0.02
85.6±0.22
84.2±0.12
1.71±0.51
2.81±0.25
H7 96.8±0.18
93.2±0.22
91.6±0.02
90.7±0.02
1.64±0.11
2.61±0.05
H8 95.6±0.22
91.8±0.14
89.9±0.12
88.7±0.22
1.48±0.12
2.49±0.41
H9 94.7±0.02
90.1±0.15
88.2±0.18
87.6±0.51
1.69±0.32
2.78±0.21
H10 96.1±0.05
92.6±0.12
90.2±0.25
89.8±0.11
1.71±0.12
2.79±0.33
H11 95.2±0.15
91.4±0.16
89.4±0.08
88.2±0.23
1.52±0.36
2.62±0.42
H12 93.9±0.03
88.6±0.04
87.3±0.02
86.4±0.36
1.58±0.41
2.57±0.04
H13 99.6±0.12
97.6±0.22
96.8±0.12
95.7±0.14
1.79±0.22
2.84±0.02
H14 98.6±0.16
96.8±0.05
94.6±0.14
93.8±0.05
1.61±0.23
2.56±0.21
H15 97.8±0.14
95.3±0.04
92.8±0.16
91.4±0.08
1.62±0.15
2.56±0.51
8.4. In-vitro mucoadhesion test
The time taken for detachment of beads from sheep stomach
mucosa was measured186,187. This was evaluated by an in-vitro
adhesion testing method, known as wash off method. The
190
mucoadhesive property of beads was compared with that of a non-
adhesive material, ethylene vinyl acetate beads.
A piece of sheep stomach mucosa (2×2 cm) was mounted onto
glass slide (3×1 inch) with cyanoacrylate glue and one more glass slide
was connected with a support. The beads (50 no) were counted and
spread over the wet rinsed tissue specimen and immediately thereafter
the support was hung on the arm of a USP tablet disintegrating test
machine as shown in photographs in Figure 8.11 (a & b). By operating
the disintegration machine the tissue specimen was given a slow
regular up and down moment. The slides move up and down in the
test fluid at 37 ± 0.50C. The number of beads adhering to the tissue
was counted at 2 h intervals up to 8 h.
Fig: 8.11 (a & b) In-vitro mucoadhesion test by usingdisintegration apparatus
191
Table 8.7: Percentage mucoadhesion data for H1-H15
Formulation code % Mucoadhesion
H1 61
H2 62
H3 69
H4 63
H5 64
H6 62
H7 64
H8 63
H9 72
H10 73
H11 71
H12 74
H13 79
H14 71
H15 74
Fig: 8.12 Percentage of mucoadhesion of Famotidine hydrogels
192
8.5 In-vitro drug release and kinetic studies
8.5.1 In-vitro drug release studies
In-vitro drug release studies of Famotidine were performed using
USP dissolution test apparatus II (paddle method). The USP
dissolution apparatus was thermostated at temperature of 37±1ºC
and stirred at rate of 50 rpm. Each 100 mg equivalent hydrogels of
every formulation were taken and placed immersed in 900 ml of pH
1.2 Hcl buffer. The aliquots of 1 ml were withdrawn at time interval of
every one hour and filtered and replaced with equal volume of
dissolution medium. The sink condition was maintained throughout
the study. The samples were analyzed spectrophotometrically at
265 nm and finally cumulative amount of drug release at various time
intervals was calculated.
193
Table 8.8: In-vitro drug release and Higuchi’s data for H1-H5
Time inh
Sqrt oftime
Cumulative % release
H1 H2 H3 H4 H5
0 0 0 0 0 0 0
1 1.000 25.4 23.4 22.9 23.4 22.8
2 1.414 32.4 29.4 32.8 32.6 31.6
3 1.732 35.6 32.6 41.2 46.5 40.4
4 2.000 41.6 40.6 51.1 52.1 50.6
5 2.236 49.2 45.2 60.2 67.7 59.8
6 2.449 54.6 53.6 67.9 70.3 67.6
7 2.646 67.4 66.4 77.8 84.5 77.4
8 2.828 74.3 72.3 85.9 90.6 85.6
9 3.000 84.4 80.4 90.6 95.6 94.5
10 3.162 91.2 88.2 94.8 99.7 98.9
11 3.317 97.4 96.4 98.6 - -
Table 8.9: Peppa’s data for H1-H5
Log time Log cumulative % release
H1 H2 H3 H4 H5
0 1.405 1.369 1.360 1.369 1.358
0.301 1.511 1.468 1.516 1.513 1.500
0.477 1.551 1.513 1.615 1.667 1.606
0.602 1.619 1.609 1.708 1.717 1.704
0.698 1.692 1.655 1.780 1.831 1.777
0.778 1.737 1.729 1.832 1.847 1.830
0.845 1.829 1.822 1.891 1.927 1.889
0.903 1.871 1.859 1.934 1.957 1.932
0.954 1.926 1.905 1.957 1.980 1.976
1.000 1.960 1.945 1.977 1.999 1.995
1.041 1.989 1.984 1.994 - -
194
Fig: 8.13. In-vitro drug release data of H1-H5
Fig: 8.14. Higuchi’s plot of H1-H5
Fig: 8.15. Peppa’s plot of H1-H5
195
Table 8.10: In-vitro drug release and Higuchi’s data for H6-H10
Time inh
Sqrt oftime
Cumulative % release
H6 H7 H8 H9 H10
0 0 0 0 0 0 0
1 1.000 20.4 18.2 23.1 25.5 24.8
2 1.414 24.2 26.4 32.5 34.1 31.8
3 1.732 29.8 34.5 42.7 44.5 40.6
4 2.000 38.6 43.7 51.4 53.7 47.2
5 2.236 48.9 50.2 60.5 62.1 53.8
6 2.449 59.2 59.1 68.2 72.5 62.8
7 2.646 71.6 62.3 78.4 83.6 72.6
8 2.828 87.5 73.8 86.2 86.8 80.6
9 3.000 93.6 87.5 94.9 93.9 88.4
10 3.162 98.7 93.6 98.8 97.9 96.5
11 3.317 - 98.5 - - -
Table 8.11: Peppa’s data for H6-H10
Log time Log cumulative % release
H6 H7 H8 H9 H10
0 1.310 1.260 1.364 1.407 1.394
0.301 1.384 1.422 1.512 1.533 1.502
0.477 1.474 1.538 1.630 1.648 1.609
0.602 1.587 1.640 1.711 1.730 1.674
0.698 1.689 1.701 1.782 1.793 1.731
0.778 1.772 1.772 1.834 1.860 1.798
0.845 1.855 1.794 1.894 1.922 1.861
0.903 1.942 1.868 1.936 1.939 1.906
0.954 1.971 1.942 1.977 1.973 1.946
1.000 1.994 1.971 1.995 1.991 1.985
1.041 - 1.993 - - -
196
Fig: 8.16. In-vitro drug release data of H6-H10
Fig: 8.17. Higuchi’s plot of H6-H10
Fig: 8.18. Peppa’s plot of H6-H10
197
Table 8.12: In-vitro drug release and Higuchi’s data for H11-H15
Time inh
Sqrt oftime
Cumulative % release
H11 H12 H13 H14 H15
0 0 0 0 0 0 0
1 1.000 21.6 20.2 28.6 22.9 25.2
2 1.414 29.2 28.8 34.8 28.8 32.1
3 1.732 31.4 30.2 40.6 38.5 40.5
4 2.000 38.6 37.4 46.2 44.4 47.4
5 2.236 47.8 46.4 52.6 54.3 54.1
6 2.449 59.9 58.6 59.8 60.8 69.8
7 2.646 74.8 72.4 68.9 76.4 80.9
8 2.828 89.6 88.9 76.2 83.6 87.4
9 3.000 94.3 94.3 86.6 89.9 90.4
10 3.162 98.4 98.8 92.6 95.2 96.3
11 3.317 - - 99.6 - -
Table 8.13: Peppa’s data for H11-H15
Log time Log cumulative % release
H11 H12 H13 H14 H15
0 1.334 1.305 1.456 1.360 1.401
0.301 1.465 1.459 1.542 1.459 1.507
0.477 1.497 1.480 1.609 1.585 1.607
0.602 1.587 1.573 1.665 1.647 1.676
0.698 1.679 1.667 1.721 1.735 1.733
0.778 1.777 1.768 1.777 1.784 1.844
0.845 1.874 1.860 1.838 1.883 1.908
0.903 1.952 1.949 1.882 1.922 1.942
0.954 1.975 1.975 1.938 1.954 1.956
1.000 1.993 1.995 1.967 1.979 1.984
1.041 - - 1.998 - -
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Fig: 8.19. In-vitro drug release data of H11-H15
Fig: 8.20. Higuchi’s plot of H11-H15
Fig: 8.21. Peppa’s plot of H11-H15
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8.5.2 In-vitro kinetics studies
Data of in-vitro release were fit into different equations and
kinetic models to explain the release kinetics of Famotidine from the
mucoadhesive hydrogels. The kinetic models used were a zero-order
equation, higuchi’s model and peppa’s models159-161. The obtained
results in these formulations were plotted in various model treatment
are as follows. I.e. Cumulative percentage release of drug Vs Square
root of time (Higuchi’s) and Log cumulative percentage release Vs Log
time (Peppas). To know the mechanism of drug release of Famotidine
from the buccal tablets the drug release data was fit into Higuchi’s
models.
To find out the mechanism of drug release from hydrophilic
matrices, the in-vitro dissolution data of each formulation with
different kinetic drug release equations. Namely Zero order: Q=K0t;
Higuchi’s square rate at time: Q=KHt1/2 and Peppas: F=Kmtn, where Q
is amount of drug release at time t, F is Fraction of drug release at
time t, K0 is zero order kinetic drug release constant, KH is Higuchi’s
square root of time kinetic drug release constant, Km is constant
incorporating geometric and structural characteristic of the tablets
and n is the diffusion exponent indicative of the release mechanism.
The correlation coefficient values (r) from Higuchi’s model indicate the
kinetic of drug release and diffusion exponent values (n) from Peppas
model indicate the mechanism of drug release.
200
Fig: 8.22. Comparative in-vitro drug release data of H1-H15
Fig: 8.23. Comparative Higuchi’s data of H1-H15
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Fig: 8.24. Comparative Peppa’s data of H1-H15
Table 8.14: Diffusion characteristics of Formulations T1-T16
Formulationcode
Correlation coefficient values (r) Diffusion exponentvalue (n)Zero Order Higuchi’s Model
H1 0.9943 0.9707 0.5893
H2 0.9712 0.9988 0.6219
H3 0.9803 0.9806 0.6414
H4 0.9750 0.9968 0.6629
H5 0.9985 0.9943 0.6667
H6 0.9775 0.9897 0.7614
H7 0.9928 0.9862 0.7251
H8 0.9880 0.9916 0.6558
H9 0.9821 0.9974 0.6199
H10 O.9964 0.9913 0.6079
H11 0.9772 0.9896 0.7149
H12 0.9892 0.9996 0.7371
H13 0.9908 0.9915 0.5434
H14 0.9907 0.9940 0.6630
H15 0.9861 0.9949 0.6298
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8.6 Comparison of in-vitro drug release with marketed product
The optimized formulation H13 in-vitro drug release data were
compared with the marketed tablet dosage form. The prepared
hydrogels showed the controlled as well as promised release than the
marketed formulations. The results were presented in table no 8.15
and represented in figure 8.25
Table 8.15: Comparison of in-vitro drug release data(H13 vs Marketed product)
Time in
h
H13 Cumulative
% Drug Release
Marketed product
Cumulative % Drug
Release
1 28.6 58.8
2 34.8 82.4
3 40.6 98.2
4 46.2 -
5 52.6 -
6 59.8 -
7 68.9 -
8 76.2 -
9 86.6 -
10 92.6 -
11 99.6 -
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Fig: 8.25. Comparative in-vitro dissolution data
(H13 vs Marketed product)
8.7 In-vivo drug release study
Six male New Zealand white rabbits (2-2.5 kg) were selected for
the in-vivo study, which was already checked for absence of any
diseases. The fore limbs and hind limbs were tied into the iron rod of
the mini operation table; so that rabbit was in dorsal
position. The optimized formulation H13 was administered orally.
Dextrose solution was transfused continuously throughout the
period of study. Periodically 1 ml of blood sample was taken
by syringe, which already contained 1 ml of heparin solution
to prevent blood clotting. These blood samples were
subjected for centrifuging at 2,500 rpm for about 30 minutes.
1 ml of supernatant was taken, and after suitable dilution,
analyzed at 265 nm using UV spectrophotometer.
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The study was approved by the Ethical committee of
Annamacharya College of pharmacy, Rajampet, Andhra Pradesh,
India, (Reg. No.1220/a/08/CPCSEA/ANCP/IAEC/14/2010).
Table 8.16: In-vivo drug release data for formulation H13
Time in h Cumulative %
drug release
1 12.66
3 21.68
6 45.83
9 68.32
11 91.66
Fig: 8.26. In-vivo drug release plot of H13
8.8. In-vitro – In-vivo Correlation
The data obtained from the in-vitro drug release of formulation
H13 is correlated with in-vivo drug release in rabbit followed by
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diffusion of drug from H13. The correlation of data was carried out by
plotting graph in excel. The graph was plotted by taking in-vitro
cumulative percentage of drug release on x-axis and in-vivo
cumulative percentage of drug release on y-axis for the same period of
time.
Table 8.17: In-vitro and in-vivo correlation data of H13
Time in h Cumulative %drug release
(in-vitro)
Cumulative %drug release
(in-vivo)0 0 0
1 28.6 12.66
3 40.6 21.68
6 59.8 45.83
9 86.6 68.32
11 99.6 91.66
Fig: 8.27. In-vitro and In-vivo correlation plot
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8.9 Stability studies as per ICH
The formulation H13 was selected and the stability studies were
carried out at accelerated condition of 40±20C, 75±5% RH conditions,
stored in desiccators, the hydrogels were packed in muslin cloth
which is covered by aluminium foil and kept in above said condition
for period of three months. The hydrogel beads were analyzed
periodically for their morphology, swelling ratio, water up take, drug
content, in-vitro mucoadhesion and in-vitro drug release. Results were
analyzed by One-way ANOVA followed by Tukey’s test. Differences
were considered statistically significant at p<0.05.
8.10 Results and discussion
The mucoadhesive hydrogels of Famotidine were prepared by
physical cross linking orifice ionic gelation process with varying
proportions of polymers like HPMC-K100, SCMC and carbopol in
combination with sodium alginate. The 2% Cacl2 solution served for
the purpose of cross linking. The composition of mucoadhesive
hydrogels were shown in the table 8.2 and the formulations before
and after drying were shown in the figure 8.2, 8.3, 8.4 of H1, H9 and
H13 respectively.
Evaluation of Famotidine mucoadhesive hydrogels
The all prepared formulation of mucoadhesive hydrogels of
Famotidine were dried at room temperature and the dried beads were
evaluated for its micromeritic properties which includes angle of
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repose, bulk density, tapped density, Carr’s Index and Hausner’s
ratio. The obtained results were presented in the table 8.3.
Equilibrium Swelling Ratio (ESR)
The swelling behavior of the polymer was reported to be crucial
for its mucoadhesive character. Hence the polymers were shown
enough mucoadhesive character to provide the controlled release of
Famotidine towards the mucosal membrane. The adhesion increases
with the degree of hydration till the point of disentanglement at the
polymer tissue surface, which leads to abrupt drop in adhesive
strength due to over hydration. The formulation H13 shows the
maximum swelling at the end of 6 h than the other formulation which
is due to more concentration of HPMC with addition of carbopol and
excess hydration of polymer. The formulation H13 having sodium
alginate, HPMC and carbopol in the ration of 1:1.5:0.5 respectively.
The data of swelling ratio were presented in the table 8.4 and in figure
8.5.
Water uptake studies
The water uptake of polymers is playing very significant role for
swelling and drug release. The drug release followed by diffusion
mechanism by the creation of pore in the hydrogel beads only after
absorbing the body fluids. The water uptake of polymer mainly
depends on the hydrophilic nature. The formulation H13 shows
maximum uptake due to high proportions of HPMC. The data of water
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uptake of all the formulations were presented in the table 8.5 and the
figure were shown in 8.6.
Gel fraction
Gel fraction is carried out to determine the gelled part and
separate the water soluble part. The data of gel fraction were
presented in the table 8.6.
Physicochemical evaluation
The all formulated hydrogels were evaluated for its
physicochemical characters like percentage yield, drug content, drug
entrapment efficiency and size analysis. The obtained results were
present in the table 8.6.
In-vitro mucoadhesion test
The in-vitro mucoadhesion test was performed by wash-off test
which indicate the ability of the formulation adhering over the
mucosa. The role of polymer is very crucial for the mucoadhesion. All
the polymers were chosen for formulation is showing good adhesion.
The data of percentage of mucoadhesion were presented in the table
8.7 and represented in the figure 8.12.
In-vitro drug release and kinetic studies
Distinguishable difference was observed in the release of
Famotidine in all formulations. The in-vitro drug release and Higuchi’s
plot have shown that the drug release followed zero order kinetics,
which was known from the regression value (r). Sodium alginate is
present in an ionized state, and as a result, the polymeric network
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gets loosened comparatively, attributing for the higher drug release.
The drug release mainly depends upon the degree of swelling, water
uptake based on hydrophilic nature of the polymer, percentage of
mucoadhesion. The data of in-vitro release of all the formulation were
presented in the table 8.8 to 8.13 and represented in the figure 8.13 to
8.21.
Data of in-vitro release were fit into different equations and
kinetic models to explain the release kinetics of Famotidine from the
buccal tablets. The kinetic models used were a zero order equation,
Higuchi’s model and Peppas models. The obtained results in these
formulations were plotted in various model treatments as cumulative
percentage release of drug versus square root of time (Higuchi’s) and
log cumulative percentage release versus log time (Peppas).
To find out the mechanism of drug release from hydrophilic
matrices, the in-vitro dissolution data of each formulation were
calculated with different kinetic drug release equations. The
mechanism of drug release by Peppas model indicates the non-Fickian
evidenced with diffusion exponent values (n). The in-vitro drug release
of optimized formulation was compared with the release pattern of
marketed product and the data are present in table 8.14, represented
in figure 8.25.
In-vivo drug release study
Based on the in-vitro evaluation study the prepared
mucoadhesive hydrogels of Famotidine (H13) was selected for in-vivo
210
evaluation by applying the hydrogels to rabbits, one of its as control
untreated. The in-vivo studies of optimized formulation shows zero
order release pattern. The results were presented in the table 8.15 and
represented in figure 8.23.
The correlation of drug release was carried out for the
therapeutic efficacy of a pharmaceutical formulation and is governed
by the factors related to in-vitro and ex-vivo, in-vitro and in-vivo
characteristics of the drug. The drug release follows zero order,
showing the correlation coefficient value 0.983, the data were
presented in the table 8.16 and shown in figure 8.27.
Stability studies as per ICH
The formulation H13 was selected and the stability studies were
carried out at accelerated condition of 40±20C, 75±5% RH conditions,
stored in desiccators, the hydrogels were packed in muslin cloth
which is covered by aluminium foil and kept for period of three
months. The hydrogel beads were analyzed periodically for their
morphology, swelling ratio, water up take, drug content, in-vitro
mucoadhesion and in-vitro drug release. Results were analyzed by
One-way ANOVA followed by Tukey’s test. Differences were considered
statistically significant at p<0.05.
8.11 Conclusion
The Famotidine mucoadhesive hydrogel beads were prepared by
orifice ionotropic gelation method is well suited for the successive
formulations. The polymers and solvent were chosen has showed more
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percentage yield of hydrogels. The polymer used as sodium alginate,
HPMC K100, SCMC and carbopol for the formulation of hydrogels
shows no significant interaction with drug evidenced by Physical
observation, DSC and FTIR studies. The physicochemical properties
were characterized by Swelling index, Water uptake studies, Gel
fraction, Size analysis, percentage yield, Drug content and Drug
entrapment efficiency. The in-vitro drug release studies were
performed all the formulations shows the controlled release pattern of
drug up to 11 h. Surface morphological studies by SEM analysis
obtained showed good spherical shape and also surface morphological
characters. In-vitro drug release was also compared with that of
marketed product. The satisfactory results were obtained in all
prepared formulations and based on the results H13 was best one
when compared to other. Good correlation was observed between in-
vitro and in- vivo profile, revealed the ability of the formulation to
reproduce the in-vitro release pattern. Hence Famotidine oral
mucoadhesive hydrogel beads could be promising one as they,
increase bioavailability, minimize the dose, reduces the side effects
and improve patient compliance and also Famotidine might be a right
and suitable candidate for oral controlled drug delivery via
mucoadhesive hydrogels.