Abstract
The effects of ethanol and polyethylene glycol 400 (PEG400) solution, additives or enhancers in the transdermal drug delivery systems, upon the skin metabolism of a prednisolone ester have been investigated in the hairless mouse skin in vitro. PEG400 was found to inhibit the bioconversion of the prednisolone ester in a dose-dependent manner. The water content in the skin (viable skin)decreased gradually when the content of PEG400 increased. The appearance rate of the metabolite, prednisolone, was approximately proportional to the water content in the viable skin contacting with the PEG400 solution. While ethanol was found to exhibit the penetration enhancement as well as the inhibition of the skin metabolism, As a result of this counterbalance of ethanol effect, the appearance rate of the metabolite following the skin bioconversion reached an maximum value at a certain concentration of ethanol. The present study suggests that the effects of additives or enhances on the skin metabolism should be carefully examined for optimizing the transdermal drug delivery systems.
