p-glycoprotein
13 interactions related to p-glycoprotein
digoxin + st. john's wort
St. John's wort revs up a gut transporter that digoxin depends on for absorption, so combining them quietly drains digoxin from the bloodstream. Because digoxin has so little room to spare, that drop can leave the drug too weak to control your heart.
apixaban + st. john's wort
St. John's wort strongly induces both CYP3A4 (apixaban's main metabolizing enzyme) and P-glycoprotein (its efflux transporter). Taken together, it speeds apixaban's breakdown and clearance, lowering blood levels and weakening clot protection, which raises the risk of stroke or thromboembolism.
verapamil + st. john's wort
St. John's wort is a potent inducer of intestinal CYP3A4 and P-glycoprotein, the same enzymes that break down verapamil before it reaches the bloodstream. Taking the two together sharply lowers verapamil's systemic exposure and can erase its therapeutic effect on blood pressure, heart rhythm, or migraine prevention.
digoxin + hawthorn
Hawthorn (Crataegus) shares digoxin's cardiac target and can cross-react with the immunoassays used to monitor digoxin, so a serum level may read falsely high or low. Controlled testing shows little change in how much digoxin reaches the bloodstream, so the practical concerns are additive cardiac effects and confounded lab monitoring rather than altered absorption.
cyclosporine + st. john's wort
St. John's wort is a potent inducer of CYP3A4 and P-glycoprotein, the enzyme and transporter that clear cyclosporine. Taking the two together markedly lowers cyclosporine blood levels, which can render the drug subtherapeutic. This has caused documented acute organ rejection in transplant recipients, making the combination a contraindication.
dabigatran + st. john's wort
St. John's wort can modestly induce the P-glycoprotein (P-gp) transporter that dabigatran depends on for absorption. With repeated use this may lower dabigatran blood levels somewhat, in theory reducing clot protection. The measured effect in human studies is weak and there are no reported thrombosis cases from the pairing, but because dabigatran is given for serious clotting conditions and the herb's effect lingers after stopping, the combination is best avoided.
simvastatin + st. john's wort
St. John's wort induces the CYP3A4 enzyme and the P-glycoprotein transporter that simvastatin depends on, sharply increasing the drug's first-pass breakdown. In a controlled crossover study of healthy volunteers, two weeks of St. John's wort substantially lowered the amount of active simvastatin reaching the bloodstream, weakening its cholesterol-lowering effect.
pomelo + tacrolimus
Pomelo contains furanocoumarins that inhibit intestinal CYP3A4 and P-glycoprotein, the systems that limit how much tacrolimus is absorbed. A documented case in a renal transplant patient showed pomelo consumption raised tacrolimus blood levels, and tacrolimus has a narrow therapeutic window where small swings can cause kidney or nervous-system toxicity, or under-immunosuppression and rejection.
seville orange + cyclosporine
Seville orange (bitter orange, Citrus aurantium) contains furanocoumarins that inhibit intestinal CYP3A4, the enzyme that breaks down cyclosporine in the gut wall. Unlike grapefruit, however, a controlled human study found that Seville orange juice did not meaningfully raise cyclosporine blood levels, because cyclosporine absorption also depends on intestinal P-glycoprotein, which Seville orange spares. Most transplant teams still advise avoiding bitter orange products as a precaution given variable furanocoumarin content and the high stakes of altered immunosuppressant levels.
cbd + tacrolimus
CBD inhibits CYP3A4, CYP3A5, and P-glycoprotein, the main pathways that clear tacrolimus. Case reports and a controlled pharmacokinetic trial show that adding CBD raises tacrolimus blood levels substantially, risking nephrotoxicity, neurotoxicity, and over-immunosuppression in transplant recipients, while stopping CBD abruptly can let levels crash and risk rejection.
tacrolimus + st. john's wort
St. John's wort induces the CYP3A4 enzyme and the P-glycoprotein transporter, which speeds up clearance of tacrolimus and lowers its blood levels, raising the risk of transplant rejection. Stopping the herb after the body has adjusted can let tacrolimus levels rebound, which has been linked to kidney toxicity.
grapefruit + sirolimus
Sirolimus is a CYP3A4 and P-glycoprotein substrate with a narrow therapeutic window and high patient-to-patient variability. The FDA-approved Rapamune label states that grapefruit juice inhibits the CYP3A4-mediated metabolism of sirolimus and must not be taken with, or used to dilute, the drug, because unpredictable rises in blood levels can cause toxicity and threaten the transplanted organ.
black pepper + propranolol
Piperine, the active alkaloid in black pepper, can inhibit intestinal P-glycoprotein and several liver enzymes that normally limit how much propranolol reaches the bloodstream. A small human study found that concentrated piperine raised propranolol's blood levels, so a stable dose may behave like a somewhat higher one, slightly amplifying its blood-pressure and heart-rate effects. Culinary pepper is not the concern; concentrated piperine supplements are.