Enhancement of Dermal Delivery of Finasteride Using Microemulsion Systems

Purpose: Finasteride is a pharmaceutical agent that treats hair loss and acne with hormonal patterns. Due to its poor water solubility, and the smaller surface area in comparison to total skin surface area, penetration of the drug into hair follicles and skin is low. The aim of this research was to formulate, characterize and evaluate in vitro skin permeability of finasteride microemulsions (MEs). Methods: Finasteride MEs were prepared using a pseudo-ternary phase diagram method with an appropriate ratio of oil mixture, surfactant-co-surfactant mixture and water. MEs containing 1% finasteride were prepared with a suitable amount of oily phase and surfactant and cosurfactant. The physicochemical properties of these MEs and in vitro skin permeability of MEs were evaluated. Results: The results showed that the mean droplet size range of ME samples was 5–17 nm and pH was 5.1–5.7. The viscosity of MEs ranged from 86.4–209.6 cps. The drug release profile showed that 49.510% of the drug was released (ME-F-6) over the 24 hours of the experiment. The kinetics of drug release from all selected MEs were approximately described by Higuchi and first-order modeling. All ME formulations with different compositions and properties significantly increased flux and permeability coefficient from rat skin. The selected MEs exhibit 99.9% finasteride after six months of storage. Conclusion: This study showed that any change in the content and composition of MEs could change the physical and chemical properties in addition to ME permeability parameters. The MEs increased permeability of the skin to finasteride.