ABSTRACT
The buccal mucosa is attracting increasing interest as a site of administration for systemic delivery of drugs because the acidic and enzyme-rich gastrointestinal (GI) milieu is bypassed and hepatic first-pass metabolism is avoided (Ho et al., 1992; Merkle and Wolany, 1992). However, an important limitation to delivery via the buccal route is that the epithelium constitutes a physical barrier to the permeability of hydrophilic, as well as some lipophilic drugs, and it also represents a biochemical barrier to enzyme labile drugs. To evaluate potential drug substances for buccal drug delivery it is necessary that both in vivo and in vitro studies are conducted. The permeability of the drug across the epithelium should be investigated in vitro along with studies of, e.g. metabolism and toxicity. For that purpose, valid in vitro models of the human buccal epithelium are required. In recent decades several different models have been used, most of which involves the use of experimental animals. The human TR146 cell culture model has been set up in our laboratory and is currently being used as an in vitro model for, e.g. permeability studies with human buccal epithelium. The TR146 cell culture model has been characterized and compared with excised buccal mucosa from man and pig by the use of Ussing chambers. In this chapter, an introduction to the barrier properties of buccal mucosa is given. In addition, the TR146 cell culture model and the porcine in vitro model are described and their applications are compared and discussed.
