ABSTRACT
The main route for the absorption of orally administered polar drugs is via the portal blood due primarily to the much greater flow than occurs with the intestinal lymphatics. This chapter describes the lymphatic transport of some different large molecular weight polar compounds after gastrointestinal dosing and the requirement for the coadministration of absorption enhancers to facilitate permeation through the mucosal barrier. The success of different strategies for targeting drugs to specific sites within the body is often dependent on the anatomical characteristics of the transport barriers. This realization has special significance in terms of lymphatic transport as there are some major anatomical differences between blood and lymphatic capillaries of the intestine. Although small molecular weight polar drugs are generally absorbed from the gastrointestinal tract via the portal blood, in certain instances the lymphatic transport of these drugs and macromolecules can be enhanced.
