Orotransmucosal drug delivery is an alternative approach to the systemic and enteral drug delivery. It avoids presystemic elimination and gastric acid hydrolysis of drugs resulting in increase in the oral bioavailability. The permeability when compared through different oral mucosa, sublingual route is greater than buccal route and buccal route is greater than palatal. The permeability of buccal mucosa is 4-4000 times greater than that of skin. It provides rich blood supply for absorption. Mucoadhesion is an important phenomenon in which two material one of which is biological in nature are held together for extended period of time by interfacial forces. Adhesion is occurring due to presence of hydroxyl, carboxyl or amine group on the molecule. The mechanism of mucoadhesion is generally divided into two steps contact stage and consolidation stage. Low molecular weight, Non- ionised species, and lipid soluble substances are most easily diffusible material across the oral epithelium. Drug diffuses more efficiently across the oral mucosa if it having high pKa value. Sometime buccal drug delivery system has required permeation enhancer to overcome problem associated with drug absorption. The permeation enhancer should have reversible effect on the epithelium it should recover its barrier properties after the drug has been absorbed. This review explains the details on buccal mucosa, mucoadhesion theories and its mechanism, and evaluations for the buccal mucoadhesive tablets.
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