What Is P-Glycoprotein (P-gp)? Drug Interactions Explained

What it means

P-glycoprotein (P-gp) is a transporter protein that acts like a pump, pushing certain substances out of cells. It is found in the gut lining, liver, kidneys and the blood-brain barrier. In the gut it limits how much of some medicines is absorbed; in the kidneys and liver it helps remove them. Medicines it handles include digoxin, dabigatran and some others.

Labels mention P-gp in their 'Drug interactions' section. A P-gp inhibitor (such as some forms of verapamil, amiodarone, clarithromycin or ketoconazole) can raise levels of medicines the pump normally removes. A P-gp inducer (such as rifampin or St John's wort) can lower them. The label may say to avoid the combination, adjust the dose or monitor.

P-gp is a transporter, not an enzyme. It often works alongside CYP3A, so many medicines that affect one also affect the other, which is why labels frequently mention them together.

Where you may see it

• The 'Drug interactions' and 'Clinical pharmacology' sections of labels
• Anticoagulant and digoxin labels
• Pharmacist interaction checks