INTERACTION OF A LECITHIN MICROEMULSION GEL WITH HUMAN STRATUM-CORNEUM AND ITS EFFECT ON TRANSDERMAL TRANSPORT

A soybean lecithin microemulsion gel has been studied as a possible ma trix for transdermal drug delivery. This gel is transparent and viscou s, and it is composed of soybean phosphatidylcholine (lecithin), isopr opyl palmitate and a small amount of water. In vitro percutaneous pene tration studies of two anti-inflammatory drugs, indomethacin and diclo fenac, dissolved in the gel-system resulted in steady state fluxes of about 1 mu g h(-1) cm(-2). In order to estimate the function of the ge l as a potential transdermal penetration enhancing system, interaction studies with isolated human stratum corneum were performed using Four ier transform infrared spectroscopy (FTIR), differential scanning calo rimetry (DSC) as well as low-temperature scanning electron microscopy. These studies indicated that the lecithin gel, in particular isopropy l palmitate, affects the stratum corneum lipid organization even after 1-day incubation (FTIR, DSC), whereas recent in vivo human skin irrit ation tests showed no significant irritancy.