Chemical Enhancers in Buccal and Sublingual Delivery

Rapid developments in the field of molecular biology and gene technology resulted in generation of many macromolecular drugs with superior pharmacological efficacy, site specificity and devoid of toxic effects. However, the major problem for the oral delivery of these therapeutic agents is their extensive presystemic metabolism, instability in acidic environment resulting into inadequate and erratic oral absorption. Parenteral route of administration is the only establishedroute that overcomes all these drawbacks associated with these orally less/inefficient drugs. But, these formulations are costly, have least patient compliance and require repeated administration. The buccal delivery system found to be most convenient and easily accessible site for the delivery of such therapeutic agents. This route provides direct access to the systemic circulation through the internal jugular vein thus avoiding the hepatic first-pass effect and degradation in the gastrointestinal tract, ease of administration, and the ability to terminate delivery when required. The epithelium that lines the oral mucosa is a very effective barrier that restricts the membrane permeation for many drugs administered via this route, and can be a limiting factor to the absorption of drugs. The use of penetration enhancers is one approach forimproving buccal drug delivery. This requisite has fostered the study of penetration enhancers that will safely alter the permeability restrictions of the buccal mucosa. This review describes various classes of transmucosal chemical permeation enhancers such as bile salts, surfactants, fatty acids and their derivatives, chelators, cyclodextrins and chitosan along with their mechanism of action. Even though these enhancers influence drug delivery, further exploration of these compounds is required to understand their modifying action on the properties of buccal mucosa.