Establishing postprandial bio-equivalency and IVIVC for generic metformin sustained release small sized tablets

The objective of current study was to develop metformin hydrochloride modified release small sized tablets, and to evaluate its bioequivalence when compared with the reference product (Glucophage^® SR). The physicochemical properties of the formulated and reference tablets were determined and compared. The in vitro dissolution profiles of formulated tablets were obtained using bio-relevant media and IVIVC was established. Bioequivalence investigation was carried out in 32 healthy male volunteers who received a single dose 1,000 mg of both test and reference products in a randomized two-way crossover design in postprandial conditions. After dosing, serial blood samples were collected for a period of 48 h. Metformin concentration was assayed by using a validated LC–MS/MS method. The log-transformed C_max and AUC were statistically compared by analysis of variance, and the 90 % confidence intervals (CI) of the ratio of the log-transformed C_max and AUC between the most promising developed formulation and the reference product were determined. It was deduced that the dissolution rate profile of the formulated modified release small sized tablets was similar to the reference product employed in the study. Their similarity and difference factors were found to be well within the established limits. In the bioequivalence study, the difference in C_max, AUC_last and AUC_inf between the test and reference product was not statistically significant, with the 90 % CI of 100.73–116.20, 86.16–97.37 and 87.12–96.99 %, respectively. The results suggested that the metformin small tablets formulated with reduced quantity of controlled release polymer were found to be bioequivalent in the postprandial state. For these small tablets, pH 5.5 acetate buffer as a bio-relevant dissolution media for the development of IVIVC.