Formulation and Characterization of Antiepileptic Transdermal Gel

The oral route is generally preferred for patient compliance; however, it is significantly affected by hepatic first-pass metabolism, often requiring higher drug doses. To overcome these limitations, transdermal emulgels offer improved drug localization and distribution through adequate percutaneous absorption, enhancing both local and systemic therapeutic effects. The present study focuses on formulating a primidone-loaded emulgel designed to provide enhanced permeability, controlled release, and effective localized delivery via the topical route. As skin is one of the most accessible organs and a major site for topical drug administration, it supports various localized applications, including ophthalmic, vaginal, rectal, and dermal routes. In this work, primidone was quantified using a validated UV spectrophotometric method at 257 nm in phosphate buffer (pH 7.4), demonstrating linear, precise, and reproducible calibration curves. Preformulation studies confirmed that the drug was light yellow and odorless, with no detectable interactions between formulation components. Prepared emulgels were evaluated for sensory feel, color, pH, consistency, and extrudability. Among all formulations, PTEG4—containing Carbopol 940 (2 g), PVP, nutmeg oil, and mentha oil—exhibited superior performance. In-vitro release studies and kinetic modeling indicated that all formulations (PTEG1–PTEG4) followed a mechanism combining Fickian diffusion and super case-II transport (n > 0.5). PTEG4 demonstrated prolonged drug release with a t50% exceeding 15 hours, confirming its potential as a controlled-release transdermal drug delivery system for primidone.