PENETRATION ENHANCEMENT FOR POLYPEPTIDES THROUGH EPITHELIA .D. ROUTES OF DELIVERY - CASE-STUDIES .3. MECHANISTIC INSIGHTS TO BUCCAL DELIVERY OF PROTEINACEOUS SUBSTANCES

There are sufficient in vivo demonstrations that the buccal delivery of peptides is a potential alternative route of administration. Passage across the squamous epithelium occurs by simultaneous passive diffusion and metabolism. The inefficient permeability properties of peptides contribute to their low systemic bioavailability, thus requiring that peptides must be highly potent to exhibit biological activity. This review emphasizes: [1] the nature of the physical, anatomical and enzymatic barriers; [2] the interplay of biophysical factors and physicochemical properties of peptides governing transport mechanisms wherein non-peptide compounds are used as standards; [3] the roles of absorption promoters; and [4] gaps in our current approaches and understanding of peptide transport.