9 Formulation, optimization and evaluation of sustained release layer of atenolol Atenolol is a cardioselective β-blocker widely prescribed for asymptomatic condition such as hypertension. It is poorly absorbed from the lower gastrointestinal tract. The oral bioavailability of atenolol was reported to be 50%. 1 The human jejunal permeability and extent of absorption is low. Thus, it seems that an in gastric residence time may increase the extent of absorption and bioavailability of drug. The recommended adult oral dosage of atenolol is 50 mg twice daily for the effective treatment of hypertension. However, fluctuations of drug concentration in plasma may occur, resulting in side effects or a reduction in drug concentration at receptor side. As the drug is effective when the plasma fluctuations are minimized, therefore sustained release dosage form of atenolol is desirable. The short biological half life of drug (6 to 8 hr) also favors development of sustained release formulations. There are several approaches have been reported for prolonging the residence time of drug delivery system in a particular region of the gastrointestinal tract, such as floating drug delivery systems, swelling and expending systems, polymeric bioadhesive systems, swelling and expanding systems, modified shape systems, high density systems and other delayed gastric emptying devices. 3 The objective of the present investigation is to formulate floating sustained release tablets of atenolol to increase the gastric retention for better absorption and extend the drug release up to 1 hr. 9.1 Experimental material Atenolol was a gift sample from Zydus Cadila HealthCare Ltd, All HPMC grade polymers were procured from Chemdyes Corporation, Ahmedabad. All other chemicals and reagents used were of analytical grade. 9. Preparation of atenolol as sustained release layer 4 Atenolol was prepared as sustained release by using hydrophilic polymer hydrophobic polymers as well as natural polymers. Wet granulation method was employed by using organic solution Iso Propyle Alcohol (IPA) as a vehicle and Poly Vinyl Pyrolidine K 30 (PVP K- 30) as a binder. Hydrophilic polymer Hydroxy Propyle Methyle Cellulose (HPMC) of different viscosity grades was selected as hydrophilic polymer, Eudragit RSPO and Carbopol were selected as hydrophobic polymers and Xanthan gum and Guar gum were selected as natural polymers to retard the release rate. Modi Darshan A. 16 Ph.D Thesis
Table 9.1: Preliminary screening of formulation of sustained release layer of atenolol using natural, hydrophillic and hydrophobic polymers Ingredients Batches (mg) SR1 SR SR3 SR4 SR5 SR6 Atenolol 50 50 50 50 50 50 HPMC K4M 30 - - - - - HPMC K100M - 30 - - - - Carbopol - - 30 - - - Guar gum - - - 30 - - Eudragit RSPO - - - - 30 - Xanthan gum - - - - - 30 PVP K-30 15 15 15 15 15 15 DCP 00 00 00 00 00 00 Mg stearate 5 5 5 5 5 5 IPA Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. Total 300 300 300 300 300 300 Table 9.: Preliminary screening of formulation of sustained release layer of atenolol using hydrophilic polymers Ingredients Batches (mg) SR7 SR8 SR9 SR10 Atenolol 50 50 50 50 HPMC K4M 60 90 - - HPMC K100M - - 60 90 PVP K-30 15 15 15 15 DCP 170 140 170 140 Mg stearate 5 5 5 5 IPA Q.S. Q.S. Q.S. Q.S. Total 300 300 300 300 Accurately weighed atenolol, polymers and Dibasic Calcium Phosphate (DCP) were passed through 0 # sieve. Slurry of PVPK - 30 IP (5 % w/w) was prepared in IPA by gentle stirring. All the above ingredients were mixed for 15 minutes. The paste was Modi Darshan A. 17 Ph.D Thesis
added slowly in above mixer and made the lumpy mass. The prepared mass was passed with sieve # 1 and dried it at 40 o C for 1 h in an oven. Then passed this dried mass through sieve # 0. After mixing, mg. stearate (0#) was added and mixed for 5 min. The prepared blend was compressed using 1 mm concave punch in rotary tablet press machine. 9.3 Development of floating system 5 Floating system was developed using gas generating agent. Different concentration of sodium bicarbonate along with citric acid was used as gas generating agent. Accurately weighed atenolol, HPMC K100M, sodium bicarbonate, citric acid and DCP were passed through 0 # sieve. Slurry of PVP K-30 IP (5% w/w) was prepared in IPA by gentle stirring. All the above ingredients were mixed for 15 min. The paste was added slowly in above mixer and made the lumpy mass. The prepared mass was passed with sieve # 1 and dried it at 40 o C for 1 h in oven. Then passed this dried mass through sieve # 0. After mixing, Mg. stearate (0#) was added and mixed for 5 min. The prepared blend was compressed using 1 mm concave punch in rotary tablet press machine. Table 9.3: Preliminary screening of gas generating agent Ingredients Batches (mg) FL1 FL FL3 FL4 FL5 Atenolol 50 50 50 50 50 HPMC K100M 90 90 90 90 90 Xanthan gum - - - - 60 Sod.bicarbonate 30 45 60 45 45 Citric acid - - - 30 30 PVP K30 (5%) 15 15 15 15 15 DCP 110 95 80 110 5 Mg stearate 5 5 5 5 5 IPA Q.S. Q.S. Q.S. Q.S. Q.S. Total 300 300 300 300 300 Modi Darshan A. 18 Ph.D Thesis
9.4 Optimization of tablet formulation using 3 full factorial design 6 A statistical model incorporating interactive and polynomial terms was used to evaluate the responses. Y = b 0 + b 1 X 1 +b X + b 1 X 1 X + b 11 X 1 +b X [9.1] Where, Y is the dependent variables, b 0 is the arithmetic mean response of the nine runs, and b 1 is the estimated coefficient for the factor X 1. The main effects (X 1 and X ) represent the average result of changing one factor at a time from its low to high value. The interaction terms (X 1 X ) show how the response changes when two factors are simultaneously changed. The polynomial terms (X 1 and X ) are included to investigate non-linearity. HPMC K100M (X 1 ) and sodium bicarbonate (X ) were selected independent variables. The preparation and evaluation method for tablets and amount of atenolol were kept constant for all trials. A 3 randomized full factorial design was utilized in the present study. In this design two factors were evaluated, each at three levels, and experimental trials were carried out at all nine possible combinations. The design layout and coded value of independent factor is shown in Table. The factors were selected based on preliminary study. The concentration of HPMC K100M (X 1 ) and concentration of Sodium bicarbonate (X ) were selected as independent variables. Table 9.4: Full factorial design layout Batch code X 1 X F1-1 -1 F -1 0 F3-1 1 F4 0-1 F5 0 0 F6 0 1 F7 1-1 F8 1 0 F9 1 1 Modi Darshan A. 19 Ph.D Thesis
Model is fitted by carrying out multiple regression analysis and F-statistics to identify statistically significant terms. The time required for 50% drug release (t 50 ), release at 15 min (Q 15 ), release at 360 min (Q 360 ), FLT, and time required for 75% drug release (t 75 ) were selected as dependent variables. Table 9.5: Coded values for concentration of HPMC K100M and concentration of sodium bicarbonate Coded values X 1 (HPMC K100M) X (NaHCO 3 ) -1 0% 10% 0 5% 1.5% +1 30% 15% Table 9.6: Composition of factorial design batches Ingredients Batches (mg) F1 F F3 F4 F5 F6 F7 F8 F9 Atenolol 50 50 50 50 50 50 50 50 50 HPMC K100M 60 60 60 75 75 75 90 90 90 Xanthan gum 37.5 37.5 37.5 37.5 37.5 37.5 37.5 37.5 37.5 Sod.bicarbonate 30 37.5 45 30 37.5 45 30 37.5 45 Citric acid 5 5 5 5 5 5 5 5 5 PVP K30 (5%) 15 15 15 15 15 15 15 15 15 DCP 77.5 70 6.5 6.5 55 47.5 47.5 40 3.5 Mg stearate 5 5 5 5 5 5 5 5 5 IPA Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. Total 300 300 300 300 300 300 300 300 300 9.5 Evaluation of atenolol sustained release tablets 7, 8 9.5.1 Physical parameters of atenolol sustained release tablets As per I.P, prepared atenolol sustained release tablets were evaluated for various parameters like weight variation test, hardness and friability as per procedure described in sections 5.3. Results are shown in Table 9.7. Modi Darshan A. 130 Ph.D Thesis
9.5. Floating property study 9 The time taken for dosage form to emerge on surface of medium is called buoyancy lag time (BLT). Duration of time for which the dosage form constantly emerges on surface of medium called Total floating time (TFT). Floating characteristics of the prepared formulations were determined by using USP 3 paddle apparatus at a paddle speed of 50 rpm in 900 ml of a 0.1 N HCl solution at 37±0. C. 9.5.3 Dissolution studies for sustain release layer 10 In-vitro dissolution tests were carried out using USP apparatus type II (ELECROLAB TDT 06 T, Bombay). The dissolution medium consisted of 900 ml 0.1N HCl for first two h and then replaced with phosphate buffer 6.8 for rest of the period maintained at 37 ± 0.5 0 C and stirred at 50 RPM. Samples (10 ml) were withdrawn at predetermined time intervals of 1,, 4, 6, 8, 10 and 1 hr. Equal amount fresh dissolution medium, maintained at same temperature, was replaced immediately. Samples were analyzed for drug content using UV-Visible spectrophotometer at 71 nm. It was made clear that none of the ingredients used in the matrix formulation interfered with the assay. Percentage drug release was computed from prepared standard curve. The release study was conducted in the triplicate and mean values were plotted. 9.5.4 Swelling studies of sustain release layer The extent of swelling was measured in terms of percentage weight gain by the tablet. The swelling behaviors of the formulations were studied. One tablet from each formulation was exposed to ph 6.8 phosphate buffers. At the end of 1 h, tablet was withdrawn, soaked with tissue paper and weighed. Then for every hr, weight of the tablets were noted and the process continued till the end of 1 hr. Percentage weight gain by the tablet was calculated using the formula. S.I = (M t -M o /M o 100) Where, S.I = swelling index, M t = weight of tablet at time t, M 0 = Initial weight of tablet. 9.5.5 Kinetic analysis 11-16 Atenolol sustained release tablets were evaluated for kinetic analysis as per description of section 6.3.4. Modi Darshan A. 131 Ph.D Thesis
9.6 Results and discussion 9.6.1 Physical parameters Table 9.7: Evaluation of physical parameters of formulations SR1-SR6 Evaluation parameters Batches Thickness ± S.D. (mm) Hardness ± S.D. (kg/cm ) Friability (%) (n = 10) Weight variation (mg) Drug content (%) (n = 5) (n = 5) (n =0) SR1 3.36 ± 0.03 4.9 ± 0.5 0.344 304. ± 10. 96.4 SR 3.35 ± 0.04 4.8 ± 0.8 0.98 305.4 ± 7.1 98.9 SR3 3.36 ± 0.0 4.9 ± 0.4 0.45 305.8 ± 5.4 101.5 SR4 3.3 ± 0.01 4.8 ± 0.7 0.156 301.3 ± 4.5 98.98 SR5 3.3 ± 0.04 4.8 ± 0.5 0.11 300.3 ±3.7 97.90 SR6 3.8 ± 0.0 4.8 ± 0.3 0.1 301.5 ± 8.1 99.5 For preliminary screening, atenolol sustained release layer was prepared using different properties of polymers comprised of 6 batches. These all 6 different formulations were evaluated for some pharmocotechnical physical characteristics like weight variation, hardness, thickness and friability. After evaluating it was found that none of the formulation deviated more than 5% of an average weight. It confirmed the pharamcoepial limits for the same test. It was laso observed that friability of all the formulations were below 1%, which also confirmed the specifications. Hardness was found very even in all formulations. After preliminary screening, tablets prepared using 0 and 30% concentration of HPMC K4M and HPMC K100M as shown in table 9.7 and evaluated for hardness, weight variation, friability and drug content. The average weight of tablet formulations was within the range of 301-304 mg. So, all tablets passed weight variation test as the weight variation was within the pharmacopoeial limits of 5% of the weight. The weight of all the tablets was found to be uniform with low standard deviation values. Hardness of all the batches was in the range of 4.8-4.9 kg/cm which ensure good handling characteristic of all batches. The friability was less than 1% in Modi Darshan A. 13 Ph.D Thesis
all the formulations ensuring that the tablets were mechanically stable. Drug content for all the batches was found within the pharmacopoeial limits. Table 9.8: Evaluation of physical parameters of batches SR7-SR10 Evaluation parameters batches Thickness ± S.D. (mm) (n = 5) Hardness ± S.D. (kg/cm ) Friability (%) (n = 10) Weight variation (mg) ± S.D. Drug content (%) (n = 5) (n =0) SR7 3.34 ± 0.03 4.9 ± 0.3 0.44 301.5 ± 1.1 104.4 SR8 3.34 ± 0.04 4.9 ± 0.5 0.37 301.3 ± 7.7 101.9 SR9 3.35 ± 0.03 4.9 ± 0.3 0.431 304.7 ± 13. 101.5 SR10 3.34 ± 0.0 4.8 ± 0.4 0.89 303. ± 10. 99.78 After optimization of concentration of sustain release polymer i.e. HPMC K100M attempt was made to prepare atenolol floating tablet using different concentration of sodium bicarbonate alone as well as combination of it with citric acid. Prepared batches were evaluated for floating lag time and other physical parameters Table 9.9: Evaluation parameters of preliminary screening of floating approach Evaluation parameters Batches Thickness ± S.D. (mm) Hardness ± S.D. (kg/cm ) Friability (%) Wt variation (mg) ± S.D. Drug content (%) FLT (min) (n = 5) (n = 5) (n=0) FL1 3.4 ± 0.0 4.9 ± 0. 0.54 30.3±. 98.4 36 FL 3.3 ± 0.05 4.8 ± 0.3 0.67 30.5± 1. 100.9 8 FL3 3.3 ± 0.0 4.9 ± 0.3 0.531 304.7±.5 99.54 4 FL4 3.34 ± 0.03 4.9 ± 0.4 0.589 303.1± 1.8 97.78 1.3* FL5 3.0 ± 0.01 4.9 ± 0. 0.47 301.8±.7 95.63 1.5 *Complete erosion of tablet. Modi Darshan A. 133 Ph.D Thesis
The average weight of tablet formulations was within the range of 30-304 mg. So, all tablets passed weight variation test as the weight variation was within the pharmacopoeial limits of 5% of the weight. The weight of all the tablets was found to be uniform with low standard deviation values. Hardness of all the batches was in the range of 4.8-4.9 kg/cm which ensure good handling characteristic of all batches. The friability was less than 1%. All the batches were evaluated for floating property. Here tablets prepared using Sodium bicarbonate alone has FLT within 4-36 min in which FL3 batch shows least FLT because of higher concentration of Sodium bicarbonate while it is highest in tablets prepared using less concentration of Sodium bicarbonate i.e. 36 min in batch FL1. FLT more than 15 min was not desirable so to decrease the FLT combination of Sodium bicarbonate and citric acid was used in batch FL4 which shows FLT of 1.3 min. 9.6. In-vitro dissolution profile of atenolol Table 9.10: Drug release profile of batches SR1-SR6 Time (h) Cumulative Drug Release (%) SR1 SR SR3 SR4 SR5 SR6 0 0 0 0 0 0 0 8.43 65.85 51.65 6.40 1 ±0.17 ±0.63 ±0.34 ±0.33 91.03 86.74 74.11 80.68 ±0.49 ±0.69 ±0.40 ±0.53 97.48 93.08 97.13 98.5 4 ±0.51 ±0.54 ±0.59 ±0.47 98.07 98.36 100.88 98.90 6 ±0.48 ±0.87 ±0.39 ±0.36 All values are expressed as mean ± standard deviation, n=3. 53.8 ±0.3 74.03 ±0.49 96.51 ±0.45 99.38 ±0.53 56.71 ±0.3 74.96 ±0.53 9.47 ±0.41 98.07 ±0.50 Tablets prepared using 10% concentration of HPMC K4M, carbopol and guar gum can sustained the drug release up to 5 hr while tablets prepared using HPMC K100M, eudragit and xanthan gum can sustained the drug release up to 6 hr. Formulation prepared using eudragit does not show swelling during dissolution study because of hydrophobic nature of eudragit while tablets prepared using carbopol tend to stick at the bottom of the dissolution apparatus as carbopol has mucoadhesive property so chances of adhesion of floating tablet to the stomach wall prepared using carbopol. For such reason eudragit and carbopol were not selected for further study. Tablets Modi Darshan A. 134 Ph.D Thesis
prepared using guar gum sustained the drug release up to 5 hr. To sustain the drug release up to 1 hr higher concentration of guar gum was required and as it is a natural polymer its property may be differ depending on the manufacturer and availability of raw material so Guar gum was not selected for further study. Xanthan gum can sustain the drug release up to 6 hr and has good matrix integrity. So, it may be used to maintain the matrix integrity of the floating tablet. HPMC K4M in 10 % concentration sustain drug release up to 5 hr while HPMC K100M sustain the drug release up to 6 hr as it has a higher viscosity than HPMC K4M, so combination of both the polymers may be used if HPMC K100M alone cannot sustain the drug release up to 1 hr. 10 Cumulative Drug Release (%) 100 80 60 40 0 0 0 1 3 4 5 6 7 SR1 SR SR3 SR4 SR5 SR6 Time (hr) Figure 9.1: Dissolution profile of atenolol for primary screening From the in-vitro dissolution study and above mentioned reasons HPMC K4M and HPMC K100M were selected for further study and tablets were prepared using 0% and 30% concentration of both and evaluated for drug release study and other evaluation parameters. Tablets prepared using 0% concentration of HPMC K4M sustain the drug release up to 7 hr and release 98.71%, while tablets prepared using 30% concentration of HPMC K4M could sustain the drug release up to 8 hr and release 96.99% drug after 8 hr. While tablets prepared using 0% concentration of HPMC K100M could sustain the drug release up to 11 hr and release 97.6% drug while tablets prepared using 30% concentration of HPMC K100M released 94.69% drug after 1 hr. So, increase in Modi Darshan A. 135 Ph.D Thesis
concentration of polymer can sustain the drug release. Viscosity of HPMC K4M was less compared to HPMC K100M and HPMC K100M can provide the drug release up to 1 hr. Therefore, HPMC K100M was selected for further study and attempt was made to prepare floating tablet. Table 9.11: Dissolution profile of batches SR7-SR10 Time Cumulative Drug Release (%) (min) SR7 SR8 SR9 SR10 0 0 0 0 0 1 39.13 33.68.9 19.07 ±0.50 ±0.56 ±0.47 ±0.45 84.60 64.75 35.61 3.18 ±0.49 ±0.33 ±0.53 ±0.35 4 93.0 86.76 5.41 48.47 6 ±0.3 97.6 ±0.56 8 - ±0.3 96.3 ±0.9 96.99 ±0.80 10 - - ±0.70 64.89 ±0.60 78.08 ±0.55 9.4 ±0. 1 - - - All values are expressed as mean ± standard deviation, n=3. ±0.31 59.95 ±0.46 77.03 ±0.57 88.08 ±0.6 94.69 ±0.56 10 Cumulative Drug Release (%) 100 80 60 40 0 SR7 SR8 SR9 SR10 0 0 4 6 8 10 1 14 Time (h) Figure 9.: Dissolution profile of atenolol using HPMC as polymer Modi Darshan A. 136 Ph.D Thesis
9.7 Optimization using 3 full factorial design 9 9.7.1 Precompression parameters of factorial formulations The blend of powder was prepared using all possible formulation of 3 full factorial design and evaluated for evaluation parameters like Angle of Repose, Bulk density, Tapped density, Carr s index and Hausner s ratio. The method for measurement of angle of repose, bulk density, tapped density; Carr s index and Hausner s ratio are given in section. Angle of repose of all batches varies from 3.1 to 8.3. Angle of repose less than 30 indicates good flow property. Compressibility index vary from 17.4% to 5.5 % which shows good to fair compressibility. Hausner s ratio varies from 1.5 to 1.34. Hausner s ratio between 1.-1.4 indicates good compressibility. Here all these results showed good flow property and compressibility which is favorable for tablet compression. Table 9.1: Evaluation of precompression properties of batches F1-F9 Batches Angle of repose(θ) Bulk density (gm/cm 3 ) Tapped density(gm/cm 3 ) Carr s index (%) Hausner s ratio F1 7.4±1.4 0.58±0.03 0.74±0.01 1.3±1.5 1.34±0.1 F 5.3±1.4 0.56±0.04 0.7±0.04 4.6±1.3 1.7±0.3 F3 7.0±1.6 0.53±0.07 0.67±0.05 0.8±1.7 1.5±0.4 F4 3.1±1.3 0.56±0.06 0.68±0.04 1.0±1.5 1.31±0. F5 4.4±1.7 0.57±0.0 0.73±0.03.5±1.4 1.34±0.1 F6 6.±1.4 0.54±0.03 0.74±0.05 5.5±1.3 1.7±0.6 F7 8.3±1. 0.58±0.04 0.75±0.04 19.4±1.3 1.9±0. F8 7.7±1.5 0.57±0.08 0.75±0.03 17.4±1.6 1.5±0.6 F9 3.1±1.6 0.59±0.06 0.67±0.04 1.4±1.5 1.5±0.1 All values are expressed as mean ± standard deviation, n=3. 9.7. Physical parameters of factorial formulations The average weight of tablet formulations was within the range of 300-304 mg. So, all tablets passed weight variation test as the % weight variation was within the pharmacopoeial limits of 7.5% of the weight. The weight of all the tablets was found to be uniform with low standard deviation values. The mean tablet thickness (n=5) were uniform in all batches with values ranging between 3.30-3.38 mm. These values Modi Darshan A. 137 Ph.D Thesis
thus indicate uniformity within batch and batch to batch. The measured hardness of tablets of each batch ranged between 4.8-4.9 kg/cm. This ensures good handling characteristics of all batches. The friability was less than 1% in all the formulations ensuring that the tablets were mechanically stable. The percentage drug content of the all batches was found between 93.16% to 104.5%, which was within acceptable limits and indicating dose uniformity in each batch. Table 9.13: Evaluation parameters of formulations F1-F9 Batches Thickness ± S.D. (mm) (n = 5) Hardness ± S.D. (kg/cm ) (n = 5) Evaluation parameters Friability (%) (n = 10) Weight variation (mg) (n=0) Drug content (%) F1 3.3 ± 0.0 4.9 ± 0.4 0.369 30 ± 0.9 98.34 F 3.34 ± 0.04 4.9 ± 0.7 0.398 304 ± 1.0 98.78 F3 3.35 ± 0.01 4.9 ± 0.5 0.445 304 ± 1. 104.5 F4 3.3 ± 0.01 4.8 ± 0.7 0.356 301 ±0.6 94.98 F5 3.3 ± 0.03 4.9 ± 0.5 0.14 300 ±0.4 99.93 F6 3.3 ± 0.03 4.8 ± 0.4 0.31 301 ± 0.9 93.5 F7 3.30 ± 0.04 4.8 ± 0.6 0.46 30 ± 0.7 96.94 F8 3.30 ± 0.05 4.8 ± 0.5 0.87 300 ± 1.0 93.16 F9 3.38 ± 0.04 4.9 ± 0.3 0.31 304 ± 0.5 10.1 All values are expressed as mean ± standard deviation 9.7. Floating and water uptake studies of factorial formulations The swelling capacity of HPMC, and gas generated from gas generating agent helped the tablets to float. On immersion in 0.1N HCl at 37 o C, the tablets floated and remained buoyant without disintegration. All tablets float within 68-95 sec without sinking. From the results of total floating time it can be concluded that all batches showed duration of floating between 7 to 1 hr. This may be due to the amount of hydrophilic polymer. Modi Darshan A. 138 Ph.D Thesis
Table 9.14: Floating and water uptake property of formulations F1-F9 Batches Floating lag time (Sec) (n=3) Total floating time (h) Water uptake (%) F1 95±04 8 73.33 F 87±05 7 40 F3 81±05 7 66.66 F4 84±01 <1 76.66 F5 79±06 <1 93.33 F6 61±0 11 70 F7 94±05 <1 310 F8 85±05 <1 93 F9 68±01 <1 300 Water uptake study was performed on all the batches for 1 hr. From the results, it was concluded that swelling increased as time increased because the polymer gradually absorb water due to hydrophilicity of polymer. The outer most hydrophilic polymer hydrates and swells and a gel barrier are formed at the outer surface. As the gelatinous layer progressively dissolves and/or is dispersed, the hydration swelling release process is repeated towards new exposed surfaces, thus maintaining the integrity of the dosage form. In the present study, the higher swelling index was found for tablets of batch F7 containing higher concentration of HPMC K100M (30%). Thus, the viscosity of the polymer had major influence on swelling process, matrix integrity, as well as floating capability, hence from the above results it can be concluded that linear relationship exists between swelling process and viscosity of polymer. 9.7.3 In-vitro drug release study of factorial formulations In-vitro drug release data and profile of prepared tablets are shown in table 9.15. In the present study, HPMC K100M is hydrophilic in nature. In case of hydrophilic matrix system, drug release involves penetration of solvent into the matrix, hydration and swelling of the polymer and dissolution of the active ingredients and transfer of the dissolved drug and soluble matrix components into the bulk. Modi Darshan A. 139 Ph.D Thesis
Table 9.15: Cumulative percentage release of formulation of factorial formulation Time Cumulative Drug Release (%) (h) F1 F F3 F4 F5 F6 F7 F8 F9 0 0 0 0 0 0 0 0 0 0 1 54.7 ±0.5 55.41 ±0.55 59.76 ±0.41 0.74 ±0.65.35 ±0.48 3.81 ±057 15.45 ±0.34 18.66 ±0.56 4.10 ±0.33 68.59 ±0.3 69.74 ±0.4 70.04 ±0.39 33.30 ±0.37 33.79 ±0.5 40.00 ±0.59.3 ±0.35 3.96 ±0.74 31.9 ±0.74 4 80.69 8.53 83.74 46.38 47.09 55.88 37.54 37.84 43.16 ±0.39 ±0.33 ±0.39 ±0.41 ±0.34 ±0.80 6 91.09 93.19 94.19 58.90 59.63 70.09 ±0.4 ±0.66 ±0.49 ±0.41 ±0.6 ±0.6 8 98.87 73.15 74.57 83.33 - - ±0.70 ±0.47 ±0.51 ±0.5 10 84.8 86.5 93.08 - - - ±0.64 ±0.7 ±0.8 1 9.98 97.16 - - - ±0.46 ±0.57 - All values are expressed as mean ± standard deviation, n=3 ±0.43 47.6 ±0.6 56.85 ±0.56 68.81 ±0.4 75.44 ±0.5 ±0.49 49.15 ±0.59 60.57 ±0.14 71.0 ±0.51 78.31 ±0.3 ±0.8 51.1 ±0.64 63.4 ±0.49 75.03 ±0.57 85.14 ±0.49 It was observed that drug release decreased with increased concentration of HPMC K100M. Amongst 1 formulations only 5 batches sustained the drug effect of 1 hr i.e. F4, F5, F7, F8 and F9. Formulation F7, F8 and F9 were too slow to release as they released only 75 to 80% drug in 1 hr. From the result, it was concluded that concentration of hydrophilic polymers HPMC K100M along with xanthan gum was sufficient to retard the atenolol release up to 1 hr. Cumulative Drug Release (%) 10 100 80 60 40 0 0 0 4 6 8 10 1 14 Time (h) F1 F F3 F4 F5 F6 F7 F8 F9 Figure 9.3: Dissolution profile of atenolol of factorial formulations Modi Darshan A. 140 Ph.D Thesis
9.7.4 Determination of dependent variables of factorial design formulations In the present study, a 3 full factorial design was employed for optimization of Atenol tablets. Optimization was carried out by studying effect of independent variables, i.e. HPMC K-100M concentration (X 1 ) and sodium bicarbonate concentration (X ) on dependent variables. Three factorial levels coded for low, medium, and high settings ( 1, 0 and +1, respectively) were considered for three independent variables. The selected dependent variables investigated were the time required for 50% drug release (t 50 ), release at 15 min (Q 15 ), release at 360 min (Q 360 ), FLT, and time required for 75% drug release (t 75 ). The response (Yi) in each trial was measured by carrying out a multiple factorial regression analysis using the quadratic model. Table 9.16: 3 full factorial design layout for sustained release tablet Formulation code X 1 X X 1 (%) X (%) FLT (s) Response Q 15 (%) Q 360 (%) T 50 (min) T 75 (min) F1-1 -1 0 10 95 8.96 91.09 43 176 F -1 0 0 1.5 87 30.09 93.19 36 171 F3-1 1 0 15 81 3.35 94.19 7 159 F4 0-1 5 10 84 13.34 58.9 84 517 F5 0 0 5 1.5 79 14.70 59.63 76 485 F6 0 1 5 15 61 19.3 70.09 188 397 F7 1-1 30 10 94 4.9 47.0 39 715 F8 1 0 30 1.5 85 7.01 49.15 373 676 F9 1 1 30 15 68 8.59 51.1 348 603 Check point batch (actual value) Check point batch (practical value - - 3 13 76 18.60 81.15 17 33 - - 3 13 74 19.10 83.65 168 341 A statistical model incorporating interactive and polynomial terms was utilized to evaluate the responses. Y = b 0 + b 1 X 1 +b X + b 1 X 1 X + b 11 X 1 +b X [9.] Modi Darshan A. 141 Ph.D Thesis
Where, Y is the dependent variables, b 0 is the arithmetic mean response of the nine runs, and b 1 is the estimated coefficient for the factor X 1. The main effects (X 1 and X ) represent the average result of changing one factor at a time from its low to high value. The interaction terms (X 1 X ) show how the response changes when two factors are simultaneously changed. The polynomial terms (X 1 and X ) are included to investigate non-linearity. Formulation of desired characteristics can be obtained by factorial design application. The fitted equations for full model relating the responses of dependent variables were given below: A. FLT = 76.78.67 X 1 10.50 X 3.00 X 1 X + 10.33 X 1 3.17 X [9.3] Time required for floating for batches F1-F9 varies from 68-95 sec and showed correlation coefficient 0.9775. This showed best fit to model. From the P-value, it was concluded that X has the prominent effect (P<0.05) on FLT than X 1. Negative sign of X 1 and X in regression equation indicated the response value decreases as the amount of factor increases. B. Q 15 =15.41 11.9 X 1 +.6 X + 0.3 X 1 X +.79 X 1 + 0.53 X [9.4] The amount of drug release at 15 min from batches F1-F9 varies from 4.9%-30.09% and showed correlation coefficient 0.9967. This showed best fit to model. From the P- value, it was concluded that X 1 has the prominent effect (P<0.05) on Q15 than X. Negative sing of X 1 in regression equation indicates the response value decreases as the amount of factor increases and positive sign of X indicates response value increases as the amount of factor increases. C. T 50 = 59.11 + 167.83 X 1 6.0 X 7.0 X 1 X 46.17 X 1 14.67 X [9.5] Time required for 50% drug release from batches F1-F9 varies from 7-39 min and showed correlation coefficient 0.9884. This showed best fit to model. From the P- value, it was concluded that X 1 has the prominent effect (P<0.05) on T50 than X. Positive sign of X 1 in regression equation indicates the response value increases as the amount of factor increases and Negative sign of X indicates response value decreases as the amount of factor increases. Modi Darshan A. 14 Ph.D Thesis
D. T 75 = 477.11 + 48.00 X 1 41.56 X 3.75 X 1 X 49.67 X 1 16.17 X [9.6] Time required for 75% drug release from batches F1-F9 varies from 159-715 min and showed correlation coefficient 0.9968. This showed best fit to model. Positive sign of X 1 in regression equation indicates the response value increases as the amount of factor increases and Negative sign of X indicates response value decreases as the amount of factor increases. E. Q 360 = 61.91 1.8 X 1 + 3.0 X + 0.19 X 1 X + 8.13 X 1 + 1.45 X [9.7] The amount of drug release at 360 min from batches F1-F9 varies from 47.0%- 94.19% and showed correlation coefficient 0.9897. This showed best fit to model. From the P-value, it was concluded that X 1 has the prominent effect (P<0.05) on Q360 than X. Negative sign of X 1 in regression equation indicates the response value decreases as the amount of factor increases and positive sign of X indicates response value increases as the amount of factor increases. Check point batch was prepared as shown in Table 9.16 using X 1 = 3% (HPMC K100M concentration) and X =13% (sodium bicarbonate concentration). The observed responses were determined practically and results were compared with values generated from full model polynomial equation. Comparison of these values indicates good fit and validationof polynomial equation. 9.7.5 Analysis of variance Table 9.17: Analysis of Variance for response FLT Source Sum of Squares Degrees of Freedom Mean Square F Value P Value Model Significant/Non signifi-cant Relative to Noise Model 973.78 5 194.76 6.03 0.011 Significant X 1 4.67 1 4.67 5.70 0.047 Significant X 661.50 1 661.50 88.4 0.00 Significant Residual.44 3 7.48 - - - Core 996. 8 - - - - Total R 0.9775 Modi Darshan A. 143 Ph.D Thesis
Table 9.18: Analysis of Variance for response Q 15 Source Sum of Squares Degrees of Freedom Mean Square F Value P Value Model Significant/Non significant Relative to Noise Model 899.36 5 179.87 183.33 0.0006 Significant X 1 85.8 1 85.8 868.6 <0.0001 Significant X 30.74 1 30.74 31.33 0.0113 Significant Residual.94 3 0.98 - - - Core 90.31 8 - - - - Total R 0.9967 Table 9.19: Analysis of Variance for response T 50 Source Sum of Squares Degrees of Freedom Mean Square F Value P Value Model Significant/Non significant Relative to Noise Model 177953.1 5 35590.6 50.96 0.004 Significant X 1.690E 1 1.690E 4.0 0.0005 Significant 1 +005 +005 X 4056.00 1 4056.00 5.81 0.0350 Significant R 0.9884 Residual 095.1 3 698.37 - - - Core Total 180048. 8 - - - - Table 9.0: Analysis of Variance for response T 75 Source Sum of Squares Degrees of Freedom Mean Square F Value P Value Model Significant/Non significant Relative to Noise Model 387070 5 77414.0 50.96 0.0006 Significant X 3.690E 1 3.690E 4.0 0.005 Significant 1 +005 +005 X 10333.5 1 10333.5 5.81 0.001 Significant Residual 17.6 3 409.18 - - - Core Total 38887.6 8 - - - - R 0.9968 Modi Darshan A. 144 Ph.D Thesis
Table 9.1: Analysis of Variance for response Q 360 Source Sum of Squares Degrees of Freedom Mean Square F Value P Value Model Significant/Non significant Relative to Noise Model 3048.90 5 609.78 57.9 0.0035 Significant 0.9897 X 1 857.55 1 857.5 71.44 0.0005 Significant X 54.90 1 54.90 5. 0.0066 Significant Residual 31.58 3 10.53 - - - Core Total 3080.48 8 - - - - R 9.7.6 Contour plot and response surface plot design Figure 9.4: Contour plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on FLT Modi Darshan A. 145 Ph.D Thesis
Figure 9.4: Contour plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on Q 15 Figure 9.6: Contour plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on T 50 Modi Darshan A. 146 Ph.D Thesis
Figure 9.7: Contour plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on T 75 Figure 9.8: Contour plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on Q 360 Modi Darshan A. 147 Ph.D Thesis
Figure 9.9: Response surface plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on FLT Figure 9.10: Response surface plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on Q 15 Modi Darshan A. 148 Ph.D Thesis
Figure 9.11: Response surface plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on T 50 Figure 9.1: Response surface plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on T 75 Modi Darshan A. 149 Ph.D Thesis
Figure 9.13: Response surface plot showing the effect of HPMC K100M (X 1 ) and sodium bicarbonate (X ) on Q 360 9.8 Fitting of atenolol sustain release tablet in mathematical kinetic models 11-16 Table 9.: Curve fitting analysis for atenolol sustain release layer Batch Regression co efficient (R ) Zero First Highichi Korsemeyer plot Hixon Crowell order order plot (R ) n-value plot F1 0.8383 0.7940 0.9304 0.979 0.50 0.8383 F 0.741 0.6914 0.8461 0.961 0.14 0.741 F3 0.7430 0.704 0.8599 0.9377 0.195 0.7430 F4 0.9889 0.9096 0.994 0.9968 0.597 0.9889 F5 0.9947 0.993 0.9906 0.9957 0.584 0.9947 F6 0.9588 0.9136 0.9850 0.9865 0.456 0.9588 F7 0.9898 0.9116 0.9941 0.9975 0.651 0.9898 F8 0.9938 0.9379 0.9900 0.9897 0.601 0.9938 F9 0.9975 0.961 0.9780 0.988 0.500 0.9975 Modi Darshan A. 150 Ph.D Thesis
Dissolution profiles were fitted to various model and release data were analyzed on the basis of Higuchi kinetics, Zero order, Korsmeyer Peppas equation, Hixon- crowel and First order. From the Korsmeyer Peppas equation, the diffusion coefficient (n) ranges from 0.195 to 0.651. Batches F4, F5, F7 and F8 were found to be value more than 0.5 which indicated the drug release mechanism of anamolous type and rest of the formulations followed fickian release. Regression Coefficients (R) were used to evaluate the accuracy of the fit. The R values are given in Table 9.. Drug release mechanisms follow Zero order, Higuchi order and Korsemeyer kinetic rather than First order. 9.9 Conclusion Atenolol tablets were prepared by wet granulation technique using hydrophilic, hydrophillic and natural polymers such as HPMC K4M, HPMCK100M, carbopol, eudragit RSPO, guar gum and xanthan gum. All formulations were subjected to various physical and pharmacotechnical evaluation parameters. From the preliminary trials HPMC K100M was selected as one of the independent variables as release retardant polymer because it was able to deliver sustained effect up to 1 hr. Sodium bi carbonate was selected as other independent variable for better floating properties. Final strength of tablets was fixed as 300mg incorporating 50mg of drug. A 3 factorial design was adopted to get 9 combinations in each formulation. It was found that both the independent variables i.e. amount of polymer and amount of gas generating agent had significant influence on the percentage drug release and buoyancy time. The floating dual retard tablets were evaluated for various physical and pharmacotechnical parameters like weight variation, hardness, friability, drug content, in vitro buoyancy and dissolution studies. Batch F5 (5% HPMC K100M and 1.5% sodium bicarbonate) was considered as sustained release part to prepare dual retard tablet as it was able to release the drug up to 1 hr with buoyancy. Batch F5 was followed by zero order drug release and diffusion mechanism of dissolution. 9.10 References 1. Melander, A, Stenberg P, Liedholm H, Schersten B, Wahlin-Boll E. 1979. Food induced reduction in bioavailability of atenolol. Eur J Clinical Pharmacology 16: 37 330.. Amidon GL, Lennernas H, Shah VP, Crison JR. 1995. A theoretical basis for a biopharmaceutics drug classification: the correlation of in-vitro drug product dissolution and in vivo bioavailabitlity. Pharm Res.1: 413 40. Modi Darshan A. 151 Ph.D Thesis
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