Mucoadhesive microspheres: a promising tool in drug delivery

Mucoadhesive polymers have recently gained interest among pharmaceutical scientists as a means of improving drug delivery by promoting the residence time and contact time of the dosage form with the mucous membranes. Mucoadhesion is the process whereby synthetic and natural polymers adhere to mucosal surfaces in the body. If these materials are then incorporated into pharmaceutical formulations, drug absorption by mucosal cells may be enhanced or the drug will be released at the site for an extended period of time. Microspheres, in general, have the potential to be used for targeted and controlled release drug delivery; however, coupling of mucoadhesive properties to microspheres has additional advantages like, a much more intimate contact with the mucus layer, efficient absorption and enhanced bioavailability of the drugs due to a high surface to volume ratio. The present review describes the potential applications of mucoadhesive microspheres as a novel carrier system to improve drug delivery by various routes of administration like buccal, oral, nasal, ocular, vaginal and rectal, either for systemic or for local effects. The mucoadhesive polymers, methods of preparation of microspheres and their in vitro and in vivo evaluation are also described.