Buccal delivery for peptide drugs

Abstract

The non-parenteral delivery of peptides via mucosal routes is essential for the enlargement of the therapeutic benefit of various oligopeptides. Among the routes under discussion the buccal mucosa was found to allow permeation of therapeutically relevant doses, e.g. with insulin, oxytocin, vasopressin analogs, protirelin, and octreotide. However, the overall permeability is relatively low, currently still rendering the buccal mucosa a secondary choice in mucosal peptide delivery. The bioavailability of buccal delivery has turned out to be more or less disappointing, usually being in the range of one or more orders of magnitude lower than found with other mucosal sites, in particular with the nasal mucosa. Demonstrations of how the buccal permeability may be raised, mainly concentrate on the use of absorption enhancers. In fact, major success was achieved by simultaneous administration of compounds which have been shown to be effective enhancers with other epithelia as well. More tissue-specific approaches are scarce. Typical are attempts to affect the proteoglycan matrix surrounding the epithelial cells. Another strategy is inhibition of local peptidase activity. Based on permeability considerations alone there would have been frustration enough to make research on buccal peptide delivery a low priority area. But it is because of the excellent accessibility of the absorption site, the elegance of muco-adhesive dosage forms, the prospects of high patient acceptance, and, in particular, the robustness of this tissue and its fast cellular turn-over, that will lead to continuing interest in this area. Under the aspect of its ability to rapid recovery, the toxicological issue of absorption enhancers may be not as dramatic with the buccal epithelium as with other mucosal sites.