Recent developments in the use of bioadhesive systems for delivery of drugs to the oral cavity.

The delivery of therapeutic agents to, or via, the oral cavity is limited by the efficient removal mechanisms that exist in this area. Bioadhesive formulations have been developed to allow prolonged localized therapy and enhanced systemic delivery. The oral mucosa however, while avoiding first-pass effects, is a formidable barrier to drug absorption, especially for "biopharmaceutical" products arising from the recent innovations in genomics and proteomics. Bioadhesive polymers are typically hydrophilic macromolecules containing numerous hydrogen-bonding groups. Second-generation bioadhesives include modified or new polymers that allow enhanced adhesion and/or drug delivery, along with site-specific ligands such as lectins. Over the last 20 years, a range of bioadhesive formulations have been developed for the oral cavity, but only comparatively few have found their way onto the market. This review will consider some recent developments in the use of bioadhesive buccal systems, notably the development of new polymers, advanced delivery systems, and the exploitation of the multifunctional properties of some bioadhesives.