Development and in vitro in vivo testing of mucoadhesive buccal patches releasing benzydamine and lidocaine

Mucoadhesive patches releasing topical drugs in the oral cavity at a slow, predetermined rate may present distinct advantages over traditional dosage forms such as mouthwashes, oral gels and lozenges. The present study was concerned with the preparation and evaluation of mucoadhesive buccal patches for controlled release of benzydamine (BNZ) and lidocaine (LDC). The drugs were used as hydrochlorides, or, to reduce their solubility and improve their release characteristics, as salts with pectin or polyacrylic acid. A LDC-tannic acid complex was also prepared and tested. After an initial screening of mucoadhesive polymers, tamarind gum (TG), a polysaccharide obtained from the seeds of Tamarindus indica, was selected as the adhesive component. In vitro tests, carried out on a cell line of human buccal epithelial origin, indicated a very low sensitivity for TG. The patches, prepared by compressing appropriate mixtures containing the drug salts/complexes, lactose and TG, were tested in vitro for mucoadhesion and drug release, and in vivo on human volunteers for retention and release of BNZ. The devices containing the salts of BNZ with pectin and polyacrylic acid, and the complex of LDC with tannic acid showed zero-order release kinetics in vitro. The patches adhered for over 8 h to the upper gums of the volunteers, and were perfectly tolerated. BNZ hydrochloride was released in vivo and in vitro with practically identical profiles.