Drug Metabolism & Transporters

P-glycoprotein P-gp

TRP-glikoprotein
Also known as:ABCB1 · MDR1 · Pgp

An ATP-dependent efflux transporter (ABCB1, MDR1) that pumps a wide range of drugs out of cells, limiting their intestinal absorption and brain entry and promoting their biliary and renal excretion.

In depth

P-gp is expressed on the apical membrane of enterocytes, the canalicular membrane of hepatocytes, the luminal membrane of proximal tubular cells and the endothelium of the blood–brain barrier. It was first identified through its overexpression in multidrug-resistant tumor cells.

Its substrates and inhibitors overlap considerably with those of CYP3A4. Clinically relevant substrates include digoxin, dabigatran etexilate, edoxaban, ciclosporin, tacrolimus and loperamide; inhibitors include verapamil, amiodarone, clarithromycin, quinidine, ciclosporin and ritonavir, whereas rifampicin and St. John's wort induce it.

Clinical pearl

Starting amiodarone, verapamil or clarithromycin in a patient on digoxin can raise digoxin concentrations substantially through P-gp inhibition; levels should be monitored and a dose reduction considered.

Example drugs

Digoxin Dabigatran etexilate Loperamide Verapamil Amiodarone
TRIn Turkish

P-glikoprotein

Çok çeşitli ilaçları hücre dışına pompalayarak bağırsaktan absorpsiyonlarını ve beyne geçişlerini sınırlayan, safra ve böbrek yoluyla atılımlarını ise artıran ATP bağımlı bir dışa atım taşıyıcısıdır (ABCB1, MDR1).

P-gp enterositlerin apikal membranında, hepatositlerin kanaliküler membranında, proksimal tübül hücrelerinin lümene bakan membranında ve kan–beyin bariyeri endotelinde eksprese edilir. İlk kez çoklu ilaç direnci gösteren tümör hücrelerinde aşırı ekspresyonuyla tanımlanmıştır.

Substrat ve inhibitörleri CYP3A4'ünkilerle büyük ölçüde örtüşür. Klinik açıdan önemli substratlar arasında digoksin, dabigatran eteksilat, edoksaban, siklosporin, takrolimus ve loperamid; inhibitörler arasında verapamil, amiodaron, klaritromisin, kinidin, siklosporin ve ritonavir bulunur; rifampisin ve sarı kantaron ise P-gp'yi indükler.

Digoksin kullanan bir hastada amiodaron, verapamil veya klaritromisin başlanması P-gp inhibisyonu yoluyla digoksin konsantrasyonlarını belirgin şekilde artırabilir; düzeyler izlenmeli ve doz azaltımı düşünülmelidir.

Diğer adları:ABCB1 · MDR1
Updated 24.09.2026 0 views Educational reference — verify against current sources before clinical use.

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Drug Transporterİlaç Taşıyıcısı

A membrane protein that moves drugs across cell membranes, either into cells (uptake) or out of them (efflux), and thereby influences absorption, distribution and elimination.

 CYP3A4CYP3A4

The most abundant cytochrome P450 isoform in the human liver and small-intestinal epithelium, responsible for the oxidative metabolism of a large proportion of clinically used drugs.

 Blood–Brain BarrierKan–Beyin Bariyeri

A selective barrier formed by brain capillary endothelial cells joined by tight junctions and supported by pericytes and astrocyte end-feet, which restricts the passage of drugs and solutes from blood into the central nervous system.

 BioavailabilityBiyoyararlanım

The fraction of an administered dose that reaches the systemic circulation unchanged, and the rate at which it does so; by definition, bioavailability is 1 (100%) for an intravenous dose.

 Pharmacokinetic InteractionFarmakokinetik Etkileşim

An interaction in which one drug alters the absorption, distribution, metabolism or excretion of another, so that the concentrations of the affected drug change rather than its concentration–effect relationship.

 Narrow Therapeutic Index DrugDar Terapötik İndeksli İlaç

A drug for which small differences in dose or blood concentration may lead to serious therapeutic failure or serious adverse drug reactions.