cyp2c9
11 interactions related to cyp2c9
alcohol + warfarin
Alcohol affects warfarin in two opposing directions: acute heavy drinking slows the liver's metabolism of warfarin, which can raise INR and bleeding risk, while sustained heavy drinking induces those same enzymes and can lower INR, increasing clot risk. Alcohol also impairs platelets and can damage the liver where clotting factors are made, and intoxication raises fall risk, all of which compound the bleeding hazard.
phenytoin + st. john's wort
St. John's Wort activates the pregnane X receptor and induces drug-metabolizing enzymes (CYP3A4, CYP2C9, CYP2C19) and P-glycoprotein. Because phenytoin is cleared mainly by CYP2C9 and CYP2C19, taking St. John's Wort alongside it could speed phenytoin's breakdown and lower its blood levels, raising the theoretical risk of breakthrough seizures. Direct human data for phenytoin specifically are limited, so regulators treat this as a mechanism-based precaution rather than a documented loss of control.
glipizide + berberine
Berberine lowers blood sugar on its own and also slows the breakdown of glipizide by inhibiting the liver enzyme CYP2C9. Taken together, the two effects can stack and increase the risk of low blood sugar (hypoglycemia), which with a sulfonylurea like glipizide can be prolonged. Do not combine them without prescriber supervision.
warfarin + turmeric
Curcumin, the main active in turmeric, has antiplatelet activity that can add to warfarin's effect and raise bleeding risk. New Zealand's medicines regulator, Medsafe, issued an alert in 2018 after a patient stable on warfarin had their INR climb to a dangerously high level within weeks of starting a turmeric/curcumin product. A possible effect on the enzyme that clears warfarin has been seen only in animal and laboratory studies, not in people.
cranberry + warfarin
Cranberry contains flavonoids and polyphenols that may slow CYP2C9, the liver enzyme that clears the more potent S-enantiomer of warfarin. Multiple human case reports describe a rising INR and serious bleeding in patients who took up cranberry juice or supplements while stably anticoagulated, and the effect appears to depend on how much cranberry is consumed: randomized trials using a modest daily amount have not consistently reproduced it.
noni juice + warfarin
Noni juice (Morinda citrifolia) products vary widely in vitamin K content, and one published case of warfarin resistance was attributed to a high-vitamin K noni preparation. Noni has also been linked to drug-induced liver injury, which can secondarily destabilize warfarin. The interaction is real but rests on case reports rather than large studies.
fluconazole + warfarin
Fluconazole inhibits CYP2C9, the main enzyme that clears warfarin, so it can sharply raise warfarin's blood-thinning effect within a few days of starting, even after a single antifungal dose. Case reports document this combination causing serious and sometimes fatal bleeding.
pomegranate + warfarin
Pomegranate contains punicalagins and other polyphenols that inhibit the liver enzymes CYP2C9 and CYP3A4 in laboratory and animal studies, which would slow warfarin metabolism. Case reports describe both a raised INR after heavy or newly started pomegranate juice intake and a falling INR after stopping a habitual juice habit. The effect appears to be genuine but infrequent, and consistency of intake matters more than total avoidance.
sesame seeds + warfarin
Sesame seeds contain lignans (chiefly sesamin) that, in laboratory studies, inhibit a liver enzyme that clears warfarin. The concern is mechanistic and comes from test tubes, not from people who have been harmed.
cbd + warfarin
CBD inhibits the liver enzymes (notably CYP2C9, and also CYP3A4) that clear warfarin, especially its more potent S-enantiomer. Adding CBD to a stable warfarin regimen can slow warfarin breakdown, raise its blood level, push the INR upward, and increase bleeding risk. A published case report described a patient who needed a meaningful warfarin dose reduction after starting CBD.
hemp seeds + warfarin
Plain culinary hemp seeds (hulled or whole) contain only trace cannabinoids and little vitamin K, so they are unlikely to meaningfully change how warfarin works. The real concern is product confusion: anything labelled hemp extract, full-spectrum hemp, or CBD is a different category and can slow warfarin breakdown via the CYP2C9 enzyme, raising INR and bleeding risk.