P-glycoprotein (MDR1 / ABCB1)
Also known as: P-gp, PgP, MDR1, ABCB1, glicoproteina-P
ABC-superfamily efflux transporter located on the intestinal membrane, hepatocytes, renal tubules and the blood-brain barrier. It "pumps" drugs out of cells, limiting absorption and penetration.
Drugs that inhibit P-gp (e.g. amiodarone, clarithromycin, ketoconazole, verapamil, diltiazem) increase absorption and concentrations of substrates such as digoxin, dabigatran and tacrolimus; inducers lower them.
Substrates: digoxin, dabigatran, rivaroxaban (partial), tacrolimus, sirolimus, ciclosporin, loperamide, fexofenadine, colchicine.
Inhibitors: amiodarone, clarithromycin, erythromycin, ketoconazole, itraconazole, verapamil, diltiazem, ritonavir, ciclosporin, carvedilol.
Inducers: rifampicin, St John's wort, carbamazepine, phenytoin.
Classic interactions: digoxin + clarithromycin/amiodarone (digitalis toxicity), dabigatran + amiodarone (increased exposure), loperamide + P-gp inhibitors (respiratory depression).
DailyMed/FDA (NIH/NLM) — approved labels (digoxin, dabigatran); EMC-UK (MHRA) — SmPC
