Lecithin microemulsions for the topical administration of ketoprofen: percutaneous adsorption through human skin and in vivo human skin tolerability

The potential application of highly biocompatible o/w microemulsions as topical drug carrier systems for thepercutaneous delivery of anti-inflammatory drugs, i.e. ketoprofen, was investigated. Microemulsions were made up oftriglycerides as oil phase, a mixture of lecithin and n-butanol as a surfactant/co-surfactant system and an aqueoussolution as the external phase. To evaluate the percutaneous enhancing effect of oleic acid, this compound was usedas a component of some o/w microemulsions. The topical carrier potentialities of lecithin-based o/w microemulsionswere compared with respect to conventional formulations, i.e. a w/o emulsion, a o/w emulsion and a gel.Physicochemical characterisation of microemulsions was carried out by light scattering and zeta potential analyses.Microemulsions showed mean droplet size 35 nm and a negative zeta potential, that is −39.5 mV for the oleicacid–lecithin microemulsion and −19.7 mV for the lecithin-based microemulsion. The percutaneous adsorption ofthe various topical formulations was evaluated through healthy adult human skin, which was obtained fromabdominal reduction surgery. Ketoprofen-loaded microemulsions showed an enhanced permeation through humanskin with respect to conventional formulations. No significant percutaneous enhancer effect was observed forketoprofen-loaded oleic acid–lecithin microemulsions. The human skin tolerability of various microemulsion formulationswas evaluated on human volunteers. Microemulsions showed a good human skin tolerability.