Transdermal delivery of drugs.

Transdermal drug delivery involves the continuous administration of therapeutic molecules through the skin. It has the advantage of maintaining constant drug plasma levels and improving patient compliance. Compared to the oral route, losses in bioavailability due to first-pass liver metabolism are reduced. This paper describes the theory of transdermal drug penetration, the role of the skin, in vitro testing, examination of currently available transdermal delivery systems, and recent developments in iontophoresis, prodrugs, and penetration enhancers.