Quality Assesment/ in Vitro Bioequivalence Consideration of Some Sustained Release Diclofenac Sodium Tablets in the North Central Senatorial Zone of Nigeria

There is need for cross-substitution of sustained release diclofenac sodium tablets in Nigeria for better patient compliance. The in vitro bioequivalence of these products could be probed through determination and comparison of their drug release profiles and mechanisms/ kinetics of drug release which is the aim of this study. Five brands of sustained release diclofenac sodium tablets were purchased from the North Central Senatorial Zone of Nigeria. The tablets were evaluated for batch number, NAFDAC number, expiration date, weight uniformity, hardness, drug content, drug release profile and in vitro drug release mechanisms / kinetics. All the tablets had batch numbers, NAFDAC numbers and had not expired. Brands A, B and E tablets complied with the compendia standards for weight uniformity while brands C and D failed. The five brands had hardness values ranging from 4.1 – 5.4 Kgf. The friability of all the tablets were less than or equal to unity except for brand D tablets that had friability of 2.4 %. Brand A tablets released up to 100 % of drug content at 6 hours and brands B, C and D had 50 – 60% drug release after seven hours while brand E tablets released 100% of drug content within 30 minutes. The release profiles of the tablets were dominated by the Higuchian release kinetic which is diffusion controlled except brand E tablets whose drug release kinetic is anomalous. The mechanism of drug release for all the brands was dominated by the super case II transport with n-value greater than 0.89. The ƒ2 similarity determination of drug release profiles revealed that brand B drug release profile is similar to that of brand C and brand C is similar to brand D. The above results strongly suggest a possible bioequivalence between brand B, C and D tablets and so, they could be interchanged during therapy.