Purpose: To study the effect of some factors on the size of finasteride nano-emulsion by chemometric approach which could predict the size of nano-emulsion droplets under different conditions.

Methods: Nano-emulsions were prepared using spontaneous emulsification method which occurs when organic and aqueous phases are mixed. The organic phase was a homogeneous solution of oil (finasteride as a lipophilic drug) and water–miscible solvent with or without lipophilic surfactant (Span^® 80), while the aqueous phase consisted of water with or without hydrophilic surfactant (Tween^® 80). Chemometric approach was applied for optimizing the size of the nano-emulsion droplets. For this purpose, the effect of three experimental parameters on size was investigated by multivariant analysis. The experiments were performed according to Box-Behnken experimental design. The factors considered were sonication time (0 – 5 min), and contents of Span-80 (0 - 0.16 %) and Tween-80 (0 - 0.26 %).

Results: The regression model obtained was characterized by both descriptive and predictive ability. The method was optimized with respect to average diameter as a response, based on a defined equation

Conclusion: The Box-Behnken experimental design is a suitable tool for optimizing and testing the robustness of the method for preparing finasteride nano-emulsion.