Formulation and Characterization of Transdermal Patches of Venlafaxine HCl

Abstract

Background: Oral venlafaxine hydrochloride is widely used for depressive and anxiety disorders but is associated with dose-related adverse effects and peak–trough plasma fluctuations, and undergoes hepatic first-pass metabolism, which may contribute to tolerability limitations. Objective: To formulate venlafaxine HCl transdermal matrix patches using HPMC K15 and to evaluate the effect of polymer ratio and triethyl citrate concentration on physicomechanical properties, compatibility, dermal safety, and in-vitro release behavior. Methods: Six matrix patch formulations were prepared by solvent casting using an ethanol: dichloromethane (1:1) system with three drug-to-polymer ratios (0.5:0.7, 0.5:0.85, 0.5:1.0) and two plasticizer levels (triethyl citrate 0.05 or 0.15 mL). Patches were evaluated for weight variation, thickness, drug content, folding endurance, moisture loss/absorption, tensile strength, and related quality parameters. Drug–polymer compatibility was assessed by FTIR. Dermal irritation was tested in rabbits using Draize scoring. In-vitro release was assessed using USP apparatus II in phosphate buffer pH 7.4 at 32°C, with kinetic modeling using zero-order, first-order, Higuchi, and Korsmeyer–Peppas models. Results: Increasing HPMC ratio was associated with increased physicomechanical parameter values and slower in-vitro drug release, whereas higher triethyl citrate content was associated with improved flexibility and faster release. FTIR indicated no significant drug–polymer incompatibility, and rabbit testing showed no significant irritation. Conclusion: HPMC ratio and triethyl citrate concentration are key formulation determinants governing matrix patch quality and in-vitro release of venlafaxine HCl; further work should include quantitative statistical comparison and membrane-based permeation flux testing