ABSTRACT
The gastrointestinal (GI) tract, being rich in proteolytic enzymes, digests therapeutic proteins with the same efciency as it digests dietary proteins. The odds against peptide and protein drug delivery by the oral route are formidable. This, however, has not discouraged researchers from attempting oral delivery of peptides and proteins (Choonara et al., 2014). The oral route is the most popular and convenient route of delivery for traditional drugs (Lipka, Crison, & Amidon, 1996; Wang, 1996). Tremendous effort has thus been directed toward oral delivery of peptide and protein drugs, and some promising results have begun to appear. Broadly speaking, oral delivery refers to absorption from the buccal through the rectal mucosa. However, buccal and rectal delivery will be discussed separately in Chapter 9. In this chapter, the focus is on absorption from the small and large intestine and on strategies to avoid drug release in stomach following oral intake. The enzymatic and penetration barriers to oral delivery will be briey reviewed followed by a discussion of the approaches to overcome or minimize these barriers.
