Cytochrome P450 3A subfamily and P-glycoprotein (CYP3A/P-gp)

The Cytochrome P450 3A (CYP3A) subfamily and P-glycoprotein (P-gp) constitute a major biochemical barrier to drug absorption and disposition, often referred to as the CYP3A/P-gp interplay (PMID: 10429871). CYP3A enzymes, primarily CYP3A4, are heme-thiolate enzymes located in the endoplasmic reticulum of hepatocytes and enterocytes, where they metabolize a vast array of xenobiotics (UniProt: P08684). P-glycoprotein, an ATP-binding cassette (ABC) transporter encoded by the ABCB1 gene, acts as an efflux pump on the apical membranes of these same cells, extruding substrates back into the intestinal lumen or bile (UniProt: P08183). These two proteins share significant substrate overlap, meaning a single drug molecule is often both metabolized by CYP3A and transported by P-gp, leading to a synergistic reduction in oral bioavailability (StatPearls: P-glycoprotein). This system is a primary site for drug-drug interactions; for instance, inhibitors like ritonavir can dramatically increase the systemic exposure of co-administered substrates, while inducers like rifampin can lead to therapeutic failure (PubMed: 12130547). Consequently, this functional unit is a critical focus in clinical pharmacology for managing drug safety and efficacy.

Other names

CYP3A/ABCB1CYP3A4 and Multidrug resistance protein 1MDR1/CYP3A4 complexFirst-pass metabolism barrier

Modulation of drug bioavailability through the coordinated regulation of oxidative metabolism and active efflux transport.