Preparation of alkyl-substituted pyrrolidone derivatives and their evaluation as transdermal penetration enhancers

The preparation of novel transdermal penetration enhancers derived from 2-pyrrolidone were carried out, and the enhancing activities of drug permeation through the skin were evaluated by means of in vitro experiment. All the enhancers contain a short alkyl group, such as methyl, ethyl, propyl or butyl group, at 1-position and a dodecyl group at 3-position of 2-pyrrolidone ring. The enhancing activities were considerably influenced by the length of the short alkyl group at 1-position. 1-Propyl and 1-butyl-3-dodecyl-2-pyrrolidone showed the effective enhancement of penetration of indomethacin through the skin in 60 wt% ethanolic aqueous solution. Moreover, the similar enhancing activities of these compounds were also observed even in ethanolic vehicle.