Targeted Skin Delivery of Topically Applied Drugs by Optimized Formulation Design

This study explored the impact of various solution compositions on skin permeation of four model drugs (caffeine, minoxidil, lidocaine, and naproxen) with different lipophilicities. It was found that vehicles containing specific excipients, such as eucalyptol (EU) and oleic acid (OA), selectively enhanced the permeation of more hydrophilic compounds like caffeine and minoxidil by increasing their diffusivity in the stratum corneum. Nanoemulsions incorporating skin penetration enhancers significantly enhanced the skin penetration of caffeine and naproxen compared to aqueous control solutions. The study also demonstrated that niosomes and transferosomes showed greater penetration into the skin and across the stratum corneum, with transferosomes and oleic acid-containing liposomes significantly enhancing caffeine penetration into hair follicles. The findings provided insights into the mechanisms of chemical penetration enhancers and could help improve the design of new formulations or develop current ones.