Mori Kenji

Effect of styrene-butadiene-styrene copolymer membrane on controlling skin permeation of drugs and solvents

Abstract The usefulness of styrene-butadiene-styrene copolymer (SBS) as a membrane to maintain a constant reservoir for skin permeation of drugs that was not altered by the vehicle applied was evaluated in in vitro experiments using diffusion cells and excised hairless rat skin. Flurbiprofen and various ratios of water-ethanol mixed solvents were selected as model drug and vehicle, and the influx of the drug, ethanol and water and efflux of water through the skin were observed. The influx of ethanol from neat cthanol was about twice that of water from neat water, A decrease in the vehicle volume was observed in an in vivo experiment. Solvent transport markedly affected permeation of the drug itself. Application of an SBS membrane suppressed skin permeation of ethanol and water from the formulations and endogenous water from the body, thus keeping fluctuations of solvent (vehicle) compositions of topical formulations to a low level and resulting in an almost constant flux of flurbiprofen. Loading of positive pressure from the formulation side allowed even further control of the solvent composition. These results suggest the usefulness of SBS membrane as a rate-limiting membrane for multi-component enhancer formulations.