Abstract

Of the various routes of drug delivery, the oral route is often preferred by the patient. However, peroral administration of drugs has disadvantages such as hepatic first-pass metabolism and enzymatic degradation within the gastrointestinal tract which constitutes a hindrance to oral administration of certain classes of drugs, especially peptides and proteins. Consequently, other absorptive mucosae are often considered as potential sites for drug administration. Transmucosal routes of drug delivery (i.e., the mucosal linings of the nasal, rectal, vaginal, ocular, and oral cavity) offer distinct advantages over peroral administration for systemic drug delivery. These advantages include possible bypass of first-pass effect, avoidance of presystemic elimination within the GI tract, and, depending on the particular drug, better enzymatic flora for drug absorption. However, the mucosa surface as a site for drug delivery has limitations as well. Other than the low flux associated with mucosal delivery, a major limitation of the transmucosal route of administration is the lack of dosage form retention at the site of absorption. Consequently, bioadhesive polymers have extensively been employed in transmucosal drug delivery systems. If these materials are then incorporated into pharmaceutical formulations, drug absorption by mucosal cells may be enhanced or the drug may be released at the site for an extended period of time.  This review describes various bio/mucoadhesive polymers used in transmucosal drug delivery. Starting with introduction of bioadhesion with theories and mechanism, history, different bioadhesive polymers, characteristics of desired bioadhesive polymers, this article then proceeds to cover the various sites suitable for mucoadhesive drug delivery system followed by the factors affecting bio/ mucoadhesion.