Azelaic acid sodium salt in the formulation of microemulsions for topical applications

In order to develop alternative formulations for topical administration of azelaic acid, a bioactive molecule used in many skin disorders, microemulsions were prepared using the monosodium salt (AZA-Na) and evaluated as delivery vehicles. The formation of macroscopically homogeneous, stable, optically transparent, isotropic solutions (microemulsions) was investigated by constructing phase diagrams. A remarkable increase in the microemulsion phase was obtained in the presence of AZA-Na. Dialysis membrane experiments showed decreasing permeability to AZA-Na, and this was related to its partition at the microemulsion interface. The ability of the microemulsions to deliver the drug through the skin was evaluated in vitro using pig-skin. Skin flux and accumulation were much higher with microemulsions containing AZA-Na than with solutions or with microemulsion containing the drug in diacidic form. The results suggest that microemulsions containing AZA-Na could be used to optimize drug targeting in acne treatment.