ABSTRACT
Several drugs, such as clonidine, estradiol, fentanyl, nicotine, nitroglycerin, scopolamine, and testosterone, are available as skin patches for transdermal delivery. These patches do not use any enhancement mechanisms and are considered to be “passive” patches. Sufficient delivery to achieve therapeutic dose without any enhancement is feasible for these drugs since they are rel atively potent and have desirable physicochemical properties (small lipophilic molecules) to penetrate the skin. The scope of drug delivery via skin is limited to only a few drugs by passive delivery. However, the range of drugs that can be delivered via skin can be expanded by vari ous physical and chemical enhancement methods. The latter involves the use of chemical pen etration enhancers while the former can involve the use of ultrasonography (phonophoresis) or electricity. This chapter will discuss the electrically assisted transdermal delivery of drugs. The description “electrically assisted” is being used to refer to delivery by iontophoresis, electro osmosis, and electroporation. The topics of iontophoresis and electroporation are separately dis cussed in this book in more details as separate chapters. This brief chapter is written to provide a general overview of the field.
