Abstract

Administration of drugs via oral route is the most common and convenient. Three major factors can affect drug absorption from this route: physiologic, physicochemical and formulation. Drug absorption mainly takes place in small intestine after oral administration. Within the small intestine, there are 2 major families of proteins involved in transport that have significant roles on drugs absorption: Solute-carrier and adenosine triphosphate-binding cassette (ABC) superfamilies. There are 48 ABC transporters in humans as well as seven subfamilies: ABCA to ABCG. ABCB1, ABCC1/2, and ABCG2 are widely described for their impacts in the absorption of drugs. Polymorphism on ABC transporters can significantly affect the absorption of drugs from the gastro intestinal (GI) tract. Some polymorphisms can result in over expression of the transporter in the small intestine and hence reduce absorption of drugs and some result in reduction in expression and increase in absorption. These polymorphisms are an important cause of adverse drug reactions and therapeutic failures.

Key words: Polymorphism, adenosine triphosphate binding cassette, oral drug absorption, expression, ABC transporters.