Development and optimization of finasteride-cinnamon oil-loaded ethanol-free microemulsions for transdermal delivery

Abstract

Finasteride (FN) is an FDA-approved pharmacologic agent for androgenic alopecia in men. However, systemic adverse effects have been observed in the majority of patients, so topical formulations are preferred over oral administration. The objectives of this study were to develop and optimize ethanol-free microemulsion (ME) systems for the transdermal delivery of FN by using a Design Expert®. The components of MEs were screened. The hexagonal lattice design was used in this study. An FN-loaded ME composed of cinnamon oil (CNO) as the oil phase, Tween® 20 as the surfactant, propylene glycol as the cosurfactant and reverse osmosis water as the aqueous phase was prepared. The physicochemical characteristics of the ME, the FN content, and the in vitro skin permeation were then investigated. The response surface methodology and optimal FN-CNO-loaded MEs were estimated using Design Expert®. The optimal formulation was composed of 11.58% CNO, 58.42% surfactant mixture (Smix) and 30% water. The physicochemical characteristics of the optimal MEs were very close to the predicted values estimated by the computer software. Scanning electron microscopy images showed that the damage to hair fibers treated and not treated with optimal MEs was not significantly different. Our study successfully and optimally predicted ethanol-free ME systems for FN transdermal delivery.