Liposomes can both enhance or reduce drugs penetration through the skin.

The adequate formulation of topical vehicles to treat skin diseases is particularly complex. A desirable formulation should enhance the accumulation of the active drugs in the target tissue (the skin), while avoiding the penetration enhancement to be so large that the drugs reach the systemic circulation in toxic amounts. We have evaluated the transcutaneous penetration of three drugs chosen for their widely variable physicochemical properties: Amphotericin B, Imiquimod and Indole. We incorporated the drugs in fluid or ultra-flexible liposomes. Ultra-flexible liposomes produced enhancement of drug penetration into/through human skin in all cases in comparison with fluid liposomes without detergent, regardless of drug molecular weight. At the same time, our results indicate that liposomes can impede the transcutaneous penetration of molecules, in particular small ones.