Oral drug administration is the most favorable route of drug administration in the clinic. Intestinal transporters have been shown to play a significant role in the rate and extent of drug absorption of some, but not all, drug molecules. Due to the heterogeneous expression of multiple transporters along the intestine, the preferential absorption sites for drugs may vary significantly. In this chapter, we aim to summarize the current research on the expression, localization, function, and regulation of human intestinal transporters implicated in altering the absorption of low to medium molecular weight drug molecules. The role played by bile acid transport proteins (e.g., ASBT and OST-α/β) is included in the discussion. The synergistic action of intestinal drug metabolism and transport is also discussed. Despite the complicated regulatory factors, the biopharmaceutics drug disposition classification system (BDDCS) put forward by Wu and Benet may help us better predict the effect of transporters on drug absorption. The drug-induced toxicity in the intestine, which may result from drug-drug interaction, gut microbiota, and bile salt toxicity, is also discussed.
Keywords: BDDCS; Bile acid transport; Drug absorption; Drug-induced toxicity; Intestinal transporter.