[Improvement of Intestinal and Transmucosal Absorption of Peptide and Protein Drugs].

It is well known that the oral bioavailability of hydrophilic and macromolecular drugs is generally very poor due to their poor membrane permeability characteristics. Among these poorly absorbed drugs, peptide and protein drugs are typical poorly absorbed drugs which have low stability and poor permeability in the gastrointestinal tract. Consequently, the clinical administration of peptide and protein drugs is presently limited to administration by injection. However, such frequent administration subjects the patients to considerable pain, and there is also the possibility of the manifestation of serious side effects. Therefore, various approaches have been examined to overcome the poor absorption characteristics of these drugs. These approaches include (1) to use additives including absorption enhancers and protease inhibitors, (2) to modify the chemical structure of peptide and protein drugs, and (3) to apply dosage forms to these drugs, (4) to develop a novel administration method for these drugs that can serve as an alternative to oral and injection administration. We demonstrated that intestinal and transmucosal absorption of peptide and protein drugs could be improved by using these approaches. These approaches may give us useful basic information to improve the intestinal and transmucosal absorption of peptide and protein drugs.