IN VITRO RELEASE PERFORMANCE OF METFORMIN HYDROCHLORIDE FORMULATIONS USING THE FLOW-THROUGH CELL METHOD

Objective: The objective of this work was to evaluate the in vitro release performance of metformin hydrochloride formulations (500-mg tablets) using the hydrodynamic environment of the flow-through cell method. Results were compared with those generated by the official dissolution test (USP basket apparatus). Methods: The reference drug product and three generic formulations were tested with phosphate buffer pH 6.8 as dissolution medium. Dissolution profiles were carried out with an automated flow-through cell apparatus using laminar flow at 16 ml/min. Drug was quantified at 233 nm during 45 min. Dissolution profiles were compared with the calculation of f2 similarity factor, mean dissolution time, dissolution efficiency, t50% and t63.2%. Dissolution data were adjusted to several mathematical models such as Makoid-Banakar, Peppas-Sahlin, Weibull and Logistic. Results: With the flow-through cell method and at 45 min less than 60% of metformin hydrochloride dissolved was found, while with the USP basket apparatus, less than 75% of the drug was found. Some generic formulations showed f2>50 with both USP apparatuses, but statistical comparisons of parameters indicated significant differences between their dissolution profiles and reference. Due to variability obtained no dissolution profiles were compared by model-dependent approach. Conclusion: To demonstrate safe interchangeability between metformin hydrochloride generic formulations and reference bioequivalence studies should be performed. It is important post-marketing monitoring of the commercial formulations because health regulatory agencies of each country must ensure drug products with quality, safety, and efficacy at the lowest possible cost.