Humidity-Induced Alterations in Critical Quality Attributes of Immediate-Release Metformin Tablets: A Low-Cost Experimental Study

Metformin hydrochloride is a widely prescribed first-line antihyperglycemic agent for the management of Type 2 Diabetes Mellitus. Due to its highly water-soluble and hygroscopic nature, exposure to elevated environmental humidity may significantly influence the physicochemical stability and performance of immediate-release (IR) tablet formulations. The present study aimed to evaluate the effect of high relative humidity (RH) on the Critical Quality Attributes (CQAs) of commercially available generic Metformin 500 mg immediate-release tablets using a low-cost and accessible experimental methodology suitable for small laboratories and community pharmacy settings. Three commercially available brands of Metformin IR tablets were subjected to controlled humidity exposure using a saturated sodium chloride solution capable of maintaining approximately 75% RH within a sealed desiccator chamber. Pre- and post-exposure analyses were conducted for weight variation, hardness, friability, disintegration time, and dissolution behavior using USP-recommended methods. The results demonstrated significant moisture-induced alterations in tablet performance, including increased tablet mass due to moisture uptake, reduction in hardness, elevated friability, prolonged disintegration times, and modified dissolution profiles. Similarity factor (f₂) analysis revealed measurable deviations between fresh and humidity-exposed tablets, indicating altered release characteristics after storage under humid conditions. These findings highlight the vulnerability of Metformin tablets to moisture-induced degradation in tropical and resource-limited environments. The study further emphasizes the importance of appropriate packaging systems and affordable stability assessment techniques for ensuring product quality and therapeutic efficacy.