Tadalafil Transdermal Drug Delivery Using Microemulsion Formulation in Laboratory Model

Background and purpose: Tadalafil has gained wide clinical acceptance in treatment of erectile dysfunction due to its long treatment window and lower potential for visual impairment. Transdermal drug delivery prevents systemic elimination, drug-drug and food-drug interactions, and reduces side effects by reducing the dose of the drug. The aim of this study was to evaluate the effect of microemulsion formulation on dermatological drug delivery of Tadalafil in rat skin. Materials and methods: In this laboratory study, Tadalafil microemulsions were prepared using a phase-diagram method with an appropriate ratio of oil and water mixture. Factorial design with three variables in two levels was performed to prepare eight formulations. Microemulsions containing 0.05 Tadalafil were prepared with an appropriate amount of oil phase (Oleic acid, Transcotol P), surfactant (Tween 80 and Span 20), and co-surfactant (Propylene Glycol). The drug was dissolved in the oil phase. The physicochemical properties of these microemulsions were evaluated using Franz Cells. Results: The droplet size of microemulsions ranged less than 60 nm and the viscosity ranged between 114.2 and 239.2 cpz. Parameters, including pH, drug release percentage in two hour and 24 hours, viscosity, Tlag and Dapp were significantly associated with independent variables (P<0.05). Conclusion: The release kinetics of the drugs in selected microemulsions showed that compared to the Tadalafil solution, release occurs over time. All microemulsions significantly increase the flux coefficient and skin permeability.