Background: There are many advantages to administering drugs by routes that bypass the gastrointestinal tract. One such route is the transdermal in which the drug agent is applied to the skin in a patch or device of some type so that sufficient quantity penetrates the skin to exert a systemic effect. There are several theoretical advantages to this approach not the least of which is that the drug avoids being metabolized by the liver after absorption and that gastrointestinal irritation is avoided.
Aims: To discuss the various ways in which drugs can be persuaded to cross the skin barrier and also to discuss the adverse effects of transdermal administration. Technical advances have permitted an increasing number of drugs to be offered in the transdermal format.