The aim of this study was to develop microemulgel for skin delivery of kojic acid. Microemulsions (ME) containing either oleic acid (OA) or caprylic/capric triglycerides as the basic oily components were developed after construction of pseudoternary phase diagrams. Tween 80 was used as surfactant for oleic acid system both in presence and absence of ethanol or propylene glycol (PG) as cosurfactants. For the caprylic/capric systems, Tween 85 was the surfactant in presence or absence of ethanol as cosurfactant. Selected ME formulations were tested for transdermal delivery of kojic acid both in fluid state and after transformation into gel. Incorporation of cosurfactants expanded the microemulsion zone. The cosurfactant free ME were more viscous. Incorporation of kojic acid in ME systems increased the transdermal flux compared to saturated aqueous solution. caprylic/capric ME were more efficient than (OA) based ME. Transformation of the tested ME systems into gel produced significant enhancement in transdermal drug delivery compared with the saturated aqueous drug solution. However, the data revealed superior efficacy for the fluid ME systems over the corresponding microemulgel. In conclusion, both (OA) and caprylic/capric ME were promising for dermal and transdermal delivery of kojic acid even after gel formation.
Microemulgel; Microemulsion; Hydrophilic drug; Kojic acid; Oleic acid; caprylic/capric triglycerides.