The in vitro bioequivalence assessment using a dissolution apparatus, as specified by the United States Pharmacopeia (USP), is a critical parameter in the formulation and development of generic pharmaceutical products. This study is crucial for evaluating the interchangeability of generic drugs with their reference innovator counterparts. Post-market surveillance of generic drugs ensures consistent quality after distribution in the market. Metformin hydrochloride, a widely prescribed oral hypoglycemic agent for managing type 2 diabetes, is among the most utilized medications globally.

In the Philippines, there is a growing need to assess the bioequivalence of various generic formulations of metformin HCl f ilm coated tablets to ensure compliance with regulatory requirements. The Philippine Food and Drug Administration (FDA) mandates in vivo or in vitro bioequivalence including, dissolution profile comparison, as a prerequisite for the registration of generic drugs. This study aims to evaluate the quality and in vitro bioequivalence of metformin HCl f ilm-coated tablets available in the Philippine market by comparing their dissolution profiles against the innovator, Glucophage. This research seeks to provide insights into the interchangeability, therapeutic equivalence, and overall quality of these generic formulations, thus contributing to public health and regulatory standards.

Generic metformin HCl film-coated tablets were subjected to quality control tests, including weight variation, thickness and diameter, hardness, friability, and disintegration tests, in accordance with USP guidelines. To assess in vitro bioequivalence, dissolution testing was performed, and the concentration of the dissolved drug was determined using a microplate assay reader to measure absorbance. Dissolution profiles of the generic metformin HCl film-coated tablets were compared to that of the innovator drug, Glucophage to evaluate bioequivalence.

All tested generic metformin HCl film-coated tablets complied with USP specifications for quality control tests, except for the hardness test, where three brands failed to meet the required standards. While for dissolution testing, five out of six generic brands demonstrated acceptable dissolution profiles and were bioequivalent to the innovator drug Glucophage. However, one brand (Brand A) failed to meet the bioequivalence criteria, exhibiting a dissolution profile outside the acceptable limits.

This study demonstrates that most generic metformin HCl film-coated tablets available in the Philippine market meet the United States Pharmacopeia (USP) quality control requirements and exhibit in vitro bioequivalence with the innovator drug. However, the failure of three brands to meet the hardness specifications and the lack of bioequivalence in one brand highlight the need for stringent quality assurance and  regulatory oversight. Ensuring compliance with these standards is critical to maintaining the safety, efficacy, and therapeutic interchangeability of generic drugs. These findings emphasize the importance of continuous post-market surveillance to uphold the quality of generic medications in the market, to safeguard public health.