Enhancement of transdermal drug delivery: Chemical and physical approaches

Transdermal drug delivery has been intensively studied ol er the last two d ecades because of the many advantages offerred by this route of administrat ion. However, the number of drugs used in transdermal drug delivery systems has been somewhat limited,in part resulting from the formidable barrier to drug permeation presented by the upper layer of the skin, the stratum corn eum. In order to overcome this, different strategies have been implemented to render the skirt more permeable to drugs. These strategies include Loth chemical and physical approaches. In this review, we outline the enhancing activities and mechanisms of action of some of the more extensively studied chemical penetration enhancers (oxazolidinones, propylene glycol, and epid ermal enzymes). In addition, we discuss novel physical strategies, such as the use of microneedles or electroporation.