P-glycoprotein (P-gp)

An ATP-dependent efflux transporter encoded by the ABCB1 (MDR1) gene, expressed at pharmacological barriers including the intestinal epithelium, blood-brain barrier, renal tubules, and hepatic canaliculi. Limits oral bioavailability by pumping substrates back into the intestinal lumen and protects the CNS by restricting brain penetration. A major determinant of multidrug resistance in cancer.

أمثلة

• Digoxin efflux reduced by P-gp inhibitor quinidine
• Loperamide excluded from brain by P-gp (no CNS opioid effects)
• Cyclosporine as potent P-gp inhibitor increasing statin exposure