ABSTRACT
The uptake of oral administered drugs primarily occurs in the small intestine,which also has the capability to metabolize drugs.Both phase Ⅰ and phase Ⅱ metabolic enzymes were expressed in the intestinal mucosa,and cytochromes P450(CYP450s) are the principle enzymes attributed to the biotransformation of drugs.CYP3A and CYP2C are the most abundant subfamilies,accounting for approximately 80% and 16% of total CYP450s in the intestine.Compared to the liver,the expression and activity of CYP450 enzymes in the intestine was susceptible to inducers or inhibitors,leading to drug-drug interaction.This article reviews the expression of CYP enzymes in small intestine and the role of the gut wall in CYP-mediated xenobiotic metabolism.Possible drug-drug interactions due to induction or inhibition of CYP enzymes in the small intestine are also addressed.