COMPARATIVE ASSESSMENT OF THE PHYSICOCHEMICAL AND IN-VITRO BIOAVAILABILITY EQUIVALENCE OF CO-TRIMOXAZOLE TABLETS MARKETED IN TIGRAY, ETHIOPIA

The availability of numerous brands of co-trimoxazole in our local market today places health professionals in a difficult situation of choice of a suitable brand or the possibility of alternative use. The aim of the study was to predict the physicochemical and in-vitro bioavailability equivalence of six brands of co-trimoxazole tablets marketed in Tigray, Ethiopia. Weight uniformity, friability, hardness, disintegration, assay and dissolution profile were performed using methods described in British and United State Pharmacopoeias and all these tablets passed compendial specifications. Statistical analysis (ANOVA) of thickness, weight and disintegration data showed a significant difference (p<0.05) between generic and innovator brands. Similarly, a significant difference was found between the mean % release of trimethoprim (p<0.0002) and sulfamethoxazole (p<0.0001) of the generic and innovator brands at the pharmacopoeia specified time, 60 min. These statistical results indicated that the brands were not equivalent with respect to their in-vitro release profile. All products showed a trimethoprim % release of greater than 85% within 15 min. Model independent approach of similarity factor (f₂) showed; generic brands C (f₂=33.71), D (f₂=31.85) and E (f₂=36.33) were not bioequivalent with the innovator and so may probably not be used interchangeably. However, generic brands B (f₂=52.02) and F (f₂=77.55) were similar with the innovator and so may probably be used interchangeably. Results have shown that more than cost consideration and company reputation is required for day-to-day rational decision making in drug products sourcing.