Abstract
The oral bioavailability of water-soluble and macromolecular drugs is generally poor because they are impermeable through the intestinal mucosa. Therefore, various approaches have been examined to overcome the delivery problems of these drugs when they administered to the gastrointestinal tract and other mucosal sites. These approaches include (1) to use additives such as absorption enhancers, (2) to modify the molecular structure of these drugs to produce prodrugs and analogues, and (3) to use the dosage forms of these drugs. In addition, (4) the use of an alternative route including pulmonary administration is also promising strategy to improve the absorption of these drugs. In this study, we demonstrated that transmucosal absorption of poorly absorbable drugs could be improved by using these approaches. Therefore, these approaches may give us basic information to improve the transmucosal absorption of poorly absorbable drugs.
