Biowaiver-based in-vitro dissolution study of generic brands of metformin hydrochloride

Abstract

Metformin hydrochloride remains the cornerstone oral therapy for the treatment of type 2 diabetes mellitus (T2DM), with millions of patients relying on its sustained glycemic control and safety profile. Classified under the Biopharmaceutics Classification System (BCS) as a Class III compound—exhibiting high solubility and low permeability—it qualifies for regulatory biowaivers under stringent in-vitro dissolution criteria. These regulatory waivers eliminate the need for in-vivo bioequivalence studies, significantly accelerating the approval of generic formulations, particularly in resource-limited settings. This study evaluates and compares the in-vitro dissolution profiles of five commercially available metformin hydrochloride 500 mg tablet formulations under simulated gastrointestinal conditions. Dissolution testing was conducted using USP Apparatus II (paddle method) across three media—0.1 N HCl (pH 1.2), acetate buffer (pH 4.5), and phosphate buffer (pH 6.8)—to mimic stomach and intestinal environments. The dissolution profiles were assessed using similarity factor (f2), difference factor (f1), and dissolution efficiency (DE) as recommended by regulatory authorities. The findings reveal that while generic brands show comparable dissolution to the innovator product in selected media. In this study, almost all five formulations released more than 85% of the drug within 15 min under the three tested conditions, suggesting compliance with the “very rapidly dissolving” criterion set forth by regulatory authorities. However, variations in f1, f2, and dissolution efficiency metrics among brands indicate differences in formulation technology, excipient selection, and manufacturing consistency. This study affirms the value of robust in-vitro dissolution testing as a surrogate for bioequivalence, emphasizing its importance in regulatory science, generic drug development, and public health policy. Our results call for regulatory vigilance and formulation refinement to ensure therapeutic equivalence and support global diabetes management initiatives.