Carrier-Mediated Approaches to Drug Absorption

5 Transcellular Drug Absorption—Nondiffusional Processes 1.5.5.1 Carrier-Mediated Approaches to Drug Absorption 

Trans- and paracellular passage routes cannot explain in full the phenomena of drug absorption in the GI tract, as they cannot provide a simple explanation for the absorption of 

FIGURE 1.11 A scheme of the various absorption routes across the intestinal epithelium and cellular barriers to xenobiotics absorption. A, Transcellular absorption (plain diffusion) B, paracellular absorption C, carrier-mediated transcellular absorption D, facilitated diffusion E, the MDR and P-gp absorption barrier and F, endocytosis. (From Hunter, J. and Hirst, B.H., Adv. Drug Deliv. Rev., 25, 129, 1997. With permission.) 

Some Brush-Border Transporters Involved in Intestinal Absorption Processes, Pertinent to Gl Drug Absorption 

Vitamins folic acid, ascorbic acid (reduced and oxidized species), biotin, cholin, pantothenic acid Amino acids Di- and tripeptides Bile acids 

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