ABSTRACT
The route of drug delivery for a particular drug is of great importance for its onset, intensity, and duration of pharmacological action. Although direct placement into the bloodstream by intravenous injection can give the fastest onset, and control over intensity and duration, it is clearly not convenient nor usually desirable from a patient point of view; thus alternative routes of drug delivery become attractive. Historically, the most common alternative route of drug delivery is the oral route, presumably because of its convenience to the patient. However, this is a relatively hostile portal of entry for a drug. In addition, collecting intestinal blood vessels go directly to the liver and not to the general circulation, and thus orally absorbed drugs are subject to first-pass metabolism. For these and other reasons there has been increasing interest in other noninjectable routes of drug delivery including nasal, pulmonary, buccal, sublingual, transdermal, rectal, and vaginal. All of these portals of entry into the body, with the exception of transdermal and vaginal, are referred to as mucosal routes of delivery and are characterized by tissue with high blood flow and possessing numerous barriers to drug absorption (Fig. 1).
