Formulation and Evaluation of Transdermal Patches of Repaglinide and Metformin

Abstract

Transdermal drug delivery systems (TDDS) offer a non-invasive and patient-compliant approach for the sustained delivery of therapeutic agents into systemic circulation. In this study, transdermal patches containing Repaglinide and Metformin were formulated using the solvent casting method. Various ratios of natural polymer (guar gum) and synthetic polymers (HPMC K-100 and ethyl cellulose) were incorporated, along with diethyl tartrate as a plasticizer and dimethyl sulfoxide as a permeation enhancer. Ten formulations (F1–F10) were prepared and evaluated for their physicochemical characteristics, drug content uniformity, and in vitro release performance. All the prepared patches exhibited smooth, uniform surfaces and consistent weight (approximately 728–737 mg). They also showed acceptable moisture content between 3.3% and 6.4%, while surface pH values ranging from 5.1 to 6.4 were found to be compatible with skin, suggesting low irritation potential. Drug content analysis demonstrated uniform drug distribution within the patches, with Repaglinide content ranging from 91.6% to 98.9% and Metformin from 92.4% to 99.1%, complying with pharmacopeial requirements. In vitro dissolution studies indicated that the polymer composition had a significant impact on drug release behavior. Formulations with an optimal balance of hydrophilic and hydrophobic polymers provided a more controlled and sustained release profile. Among all formulations, F8 showed the best performance, releasing 89.03% of Repaglinide and 96.01% of Metformin over a 24-hour period. The release kinetics followed a zero-order model with a non-Fickian diffusion mechanism. In conclusion, the developed dual-drug transdermal patches demonstrate potential for enhancing drug bioavailability, reducing dosing frequency, and improving therapeutic outcomes in the treatment of type 2 diabetes mellitus. Nevertheless, further in vivo studies are required to validate their clinical applicability and efficacy.

Keywords: Transdermal patches, drug delivery system, skin permeability, penetration enhancers, sustained release, microneedles, pharmaceutical innovation.