Assessment of quality control parameters of multi-sourced metformin HCl sustained released tablets marketed in Nepal

Abstract

Background: Availability of numerous brands of metformin hydrochloride tablets places health practitioners, pharmacists and patients in a dilemma of generic substitution. Variable clinical responses to drugs and brand-to-brand inconsistencies have been reported due to counterfeiting. The objective of the study was to evaluate quality control parameters to compare the quality, safety and efficacy of nine brands of Metformin tablets available in the Nepalese market.

Methods: It was a cross-sectional study. Nine brands of Metformin HCL were collected from various retailers and were assessed for their shape, size, weight and colour and they were tested for their physicochemical equivalence through the evaluation of both official and non-official standards according to the established methods. The in-vitro release kinetics of drugs were studied by using Zero order, First order, Higuchi, Hixson-Crowell and Korsemeyer-Peppas models based on the correlation coefficient (r²) value. Descriptive statistics were calculated.

Results: Most of the metformin tablets were deviated by less than ±5% from the mean value except for brand I that showed a deviation greater than 7.51%. All brands showed the permissible deviation of ±5% except for brand F which showed a deviation of ±5.50. The amount of active ingredient in the solution for the metformin HCL tablets was within the acceptable range of USP limit of 65-85% for all brands except Brand B that showed slightly lower values of 63.28±1.69% after 6hrs. The cumulative amount of metformin release from the product at different time intervals were best fitted to First order and Hixson-Crowell models. Similarity factor analysis between the tablets for the release of Metformin HCL showed a f2 factor greater than 50 for all brands except brand H which showed f1 values 17.32, and f2 value 48.20.

Conclusion: The study showed that all the nine brands of the metformin hydrochloride sustained release tablet tested showed satisfactory results for the test employed and are pharmaceutical equivalent, except brand H as it showed dissimilar dissolution profiles to that of innovator product. As eight brands conformed to the established standards, they could be used interchangeably in clinical practice even though there was slight variation in their pharmaceutical equivalences.