The in vitro and in vivo Pharmaceutical equivalence and stability studies of some antihypertensive drugs manufactured in Bangladesh in rat model

Abstract

Background Bangladesh is a densely populated country. To meet the healthcare needs of this huge population, huge amounts of medicines are required. Again, the first objective of National Drug Policy 2005 was to ensure that common people of Bangladesh should have easy access to effective, safe and good quality drug products at affordable prices. As hypertension is a very common disorder in Bangladesh, many pharmaceutical companies are now producing antihypertensive drugs from each class. But most of the companies do not conduct bioequivalence studies and for clinical trial and bioequivalence studies, even now we depend on another country like Malaysia, India and. No data are available in regard to pharmaceutical equivalence and bioequivalence studies of antihypertensive drugs manufactured in Bangladesh. The present study is carried out to perform in vitro and in vivo pharmaceutical equivalence and stability studies in comparison with reference innovator brands of some antihypertensive drugs manufactured in Bangladesh to compare the quality, efficacy and safety of these drug products by taking reference innovator brands as standard brands. This study will also help the physicians to choice a suitable brand which is easily available, have standards of quality, efficacy and safety. Methods In vitro pharmaceutical equivalence of some antihypertensive drugs was determined by comparing general quality assessment parameters such as weight variation, hardness, % friability, disintegration time, dissolution time and the amount of active substance between test brands and their respective reference innovator brands. Times required for 50% dissolution (T50%) and 90% dissolution (T90%) were also compared between test brands and their respective reference innovator brands. Mean of % dissolution versus time graph and statistical difference factor (f1) and similarity factor (f2) were also compared using dissolution profiles of test brands and their respective reference innovator brands. In vivo pharmaceutical equivalence of some antihypertensive drugs was done by plotting plasma concentration- time curves of test brands with their respective reference innovator brands after administration of drug in rat models. Stability testing was compared between test brands and their respective reference innovator brands under stress conditions in acidic and basic conditions at different temperatures (290C, 600C and 700C). Results Experimental three brands of tablet atenolol 50 mg were randomly designated as AA, AB, AC and reference innovator brand as ARI. Eight brands of tablet Carvedilol 6.25 mg were randomly designated as CA, CB, CC, CD, CE, CF, CG, CH and reference innovator brand as CRI. Ten brands of tablet Losartan potassium 50 mg were randomly designated as LA, LB, LC, LD, LE, LF, LG, LH, LI, LJ and reference innovator brand as LRI. Four brands of tablet ramipril 5 mg were randomly designated as RA, RB, RC, RD and reference innovator brand as RRI. All test brands including their respective reference innovator brands passed the general quality assessment parameters such as weight variation, hardness, % friability, disintegration time, dissolution and % potency. Still significant variations were observed in disintegration time of test brands of tablet losartan potassium and tablet ramipril with their respective reference innovator brands. A correlation was observed between disintegration time and the rate of dissolution in this study. All test brands including their respective innovator brands were found within % weight variation test acceptance limit. Test brands of atenolol showed weight variation percentage limit between - 2.39% and + 2.77%, whereas reference innovator brand showed weight variation percentage limit between - 1.84% and + 1.40%. Test brands of carvedilol showed weight variation percentage limit between - 2.72% and + 5.87%, whereas reference innovator brand showed weight variation percentage limit between - 1.08% and + 0.92%. Test brands of losartan potassium showed weight variation percentage limit between - 4.66% and + 4.08%, whereas reference innovator brand showed weight variation percentage limit between -2.60% and +2.14%. Test brands of ramipril showed weight variation percentage limit between -2.00% and + 2.85%, whereas reference innovator brand showed weight variation percentage limit between -1.85% and +1.49%. All test brands of tablet atenolol, tablet carvedilol, tablet losartan potassium and tablet ramipril including their respective reference innovator brands were found satisfactory for hardness testing. Test brands of atenolol showed lowest hardness value hardness between 4.55 kg and 6.13 kg, whereas reference innovator brand showed hardness 5.32 kg. Hardness of test brands of carvedilol were found between 3.88 kg and 7.68 kg, whereas 6.26 kg was found for reference innovator brand. Hardness of test brands of losartan potassium were found between 6.28 kg and 9.96 kg, whereas 6.89 kg was found for reference innovator brand. Test brands of ramipril showed hardness between 7.51 and 13.19, whereas reference innovator brand showed 7.16 kg All test brands of tablet atenolol, tablet carvedilol, tablet losartan potassium and tablet ramipril including their respective reference innovator brands met the acceptance criteria for % friability test. They had % friability values less than 1%. All test brands of tablet atenolol, tablet carvedilol, losartan potassium and tablet ramipril including their respective reference innovator brands met the acceptance criteria for disintegration time. No major variations were found in disintegration time of different test brands of atenolol. They were found to disintegrate between 0.43 and 1.36 minutes, whereas reference innovator brand disintegrated in 1.44 minutes. No momentous variations were found in disintegration time of test brands of carvedilol. They disintegrated between 0.39 and 5.33 minutes, whereas innovator brand disintegrated in 0.78 minutes. Test brands with higher disintegration time were CE, CH and CG. Significant variations were found in disintegration time of test brands of losartan potassium. They were found to disintegrate between 6.52 and 15.22 minutes, whereas reference innovator brand disintegrated in 7.19 minutes. Test brands with higher disintegration time were LA, LC, LF, LH and LI, having values ˃10 minutes. Test brands of ramipril showed significant variations in disintegration time. All test brands of ramipril disintegrated between 0.71 and 10.90 minutes, whereas innovator brand disintegrated in 1.09 minutes. Test brands with higher disintegration time were RA, RB having values ˃5 minutes and RC ˃10 minutes. All test brands of tablet atenolol, tablet carvedilol, tablet losartan potassium and tablet ramipril including their respective reference innovator brands met the acceptance limit for % of dissolution. Test brands of tablet atenolol including their respective reference innovator brand attained more than 90% of dissolution within 30 minutes. Test brands of tablet carvedilol including their respective reference innovator brand achieved more than 90% of dissolution except brand CH which got more than 80% within 30 minutes. Test brands of tablet losartan potassium LA, LC, LE, LF, LG, LH and reference innovator brand LRI did more than 90% of dissolution except brands LB, LD, LI and LJ which got more than 80% within 30 minutes. Test brands of tablet ramipril including their respective reference innovator brand attained about 100% of dissolution within 30 minutes. All test brands of tablet atenolol, tablet carvedilol, tablet losartan potassium and tablet ramipril including their respective reference innovator brands met the acceptance limit for assay content. They had % potency between 99% and 103%. The mean % of drug dissolved of tablets of different test brands were compared with that of their respective innovator brands graphically by plotting the mean % of drug dissolved against time. All test brands including reference innovator of tablet atenolol released more than 80% of drug within 10 minutes. Except test brands CB, CC, CG, CH; all other brands including reference innovator brand of tablet carvedilol released more than 80% of drug within 20 minutes. Reference innovator brand and brands LC, LE, LF, and LG of tablet losartan potassium released more than 80% of drug in 20 minutes. Test brands LA, LB, LD, LH, LI, and LJ released more than 80% of drug in 30 minutes. Except brand RC; all test brands and reference innovator brand of tablet ramipril 5mg released more than 80% of drug in 10 minutes. The time required for 50% dissolution (T50%) and 90% dissolution (T90%) were determined. All test brands of tablet atenolol and also tablet ramipril including their reference innovator brands showed T50% values less than 10 minutes and T90% values less than 30 minutes. For tablet carvedilol; all test brands including reference innovator brand showed T50% values less than 10 minutes and T90% values less than 30 minutes except test brand CH. Test brand CH had T50% less than 10 minutes but T90% greater than 30 minutes. For tablet losartan potassium; test brands LA, LB, LD, LH, LI, LJ showed T50% values greater than 10 minutes whereas, other brands less than 10 minutes. Test brands LB, LD, LI showed T90% values greater than 30 minutes whereas, other brands less than 30 minutes. The mean percentage of drug dissolved of tablets of test brands and their respective reference innovator brands were used to calculate difference factor(f1) and similarity factor (f2) using the respective equations. All test brands of antihypertensive drugs showing f1 values less than 15 are acceptable in comparison with reference innovator brands. For test brands of tablet carvedilol CB and CH; f2 values were less than 50. For test brands of tablet losartan potassium LB, LD and LI; f2 values were less than 50. For test brand of tablet ramipril RC; f2 values were less than 50. Test brands with f2 values less 50 may not be equivalent to their respective reference innovator brands. In vitro dissolution profiles showed variations in availability of drug substances from test brands and reference innovators brands. All test brands of tablet atenolol; all test brands of tablet carvedilol except two brands CB & CH; all test brands of tablet losartan potassium except brands LB, LD & LI and all test brands of tablet ramipril except brand RC were observed to have T50% values less than 10 minutes, T90% values less than 30 minutes, f1 values less than 15 and f2 values more than 50. They appeared to have very good bioavailability. Test brands CB and RC showing f2 values less than 50 but T50% values less than 10 minutes, T90% values less than 30 minutes and f1 values less than 15 also seemed to have very good bioavailability. Test brands CH and LB, LD, LI having T50% values greater than 10 minutes, T90% values greater than 30 minutes and f2 values less than 50 were not equivalent to reference innovator brands in availability of drug substances. In vivo pharmaceutical equivalence study was done by plotting plasma concentration- time curves of test brands with their respective reference innovator brands after administration of drug products in rat models. The curves indicated that the tmax value for test brands and innovator brand of atenolol was 2.5 hrs and Cmax values for brands AA, AB, AC, ARI were 0.123, 0.128, 0.113, 0.129 μg/mL respectively. The tmax value for test brands and innovator brand of carvedilol was 1.5 hrs and Cmax values for brands CA, CB, CC, CD, CE, CF, CG, CH, CRI were 0.106, 0.106, 0.102, 0.103, 0.099, 0.096, 0.096, 0.098, 0.090, 0.106 μg/mL, respectively. The tmax value for test brands and innovator brand of losartan potassium was 1.5 hrs and Cmax values for brands LA, LB, LC, LD, LE, LF, LG, LH, LI, LJ, LRI were 0.122, 0.123, 0.126, 0.118, 0.122, 0.123, 0.118, 0.123, 0.117, 0.120, 0.124 μg/mL, respectively. The tmax value for test brands and innovator brand of ramipril was 2.5 hrs and Cmax values for brands RA, RB, RC, RD, RRI were 0.047, 0.061, 0.058, 0.053, 0.063 μg/mL, respectively. Comparing in vivo Cmax and tmax values of test brands with their respective innovators, all antihypertensive testing brands may be considered equivalent to their respective reference innovator brands. Stability studies of test brands of tablet atenolol, tablet carvedilol, tablet losartan potassium and tablet ramipril including their respective innovator brands were done by stress degradation in acidic and basic conditions at different temperatures (290C, 600C and 700C). Data showed no significant degradation of test brands and also their respective reference innovator brands. So, all antihypertensive test brands also may be considered equivalent to respective reference innovator brands regarding stability. In conclusion, this study indicated that except test brands CH, LB, LD and LI; all other test brands may be considered in vitro and in vivo pharmaceutically equivalent to their respective reference innovator brands and also equivalent in case of stability. These brands may be similar in quality, efficacy, safety and may be used interchangeably. But test brands CH, LB, LD and LI are not similar to their respective reference innovator brands and cannot be used interchangeably.