Analysis of the pretreatment effect of ethanol on the stratum corneum- and hair follicular-penetration of drugs using the hair follicle-plugging method.

The hair follicle-plugging method was used to analyze the effects of EtOH on skin permeation pathways. In vitro permeation experiments were performed on 4 model drugs [isosorbide mononitrate (ISMN), ionized lidocaine (ionized LC), fluorescein (FL), and fluorescein isothiocyanate (FITC)-dextran 4 kDa (FD-4)] using excised pig ear skin. The skin permeations of ionized LC, FL, and FD-4 were decreased by hair follicle-plugging. Hair follicle-plugging prevented the skin permeation of FL and FD-4 in EtOH-pretreated skin, but did not prevent that of ISMN. On the other hand, the effect of hair follicle-plugging on the permeation of ionized LC was different among the pretreatment conditions. These results indicate that the EtOH pretreatment greatly affected the aqueous pathway in the stratum corneum and hair follicles.