
Ingestion of large quantities of foods high in vitamin K content (see list in food sources for specific nutrients) may antagonize the anticoagulant effect of warfarin. ↑ bleeding risk with anise, arnica, chamomile, clove, dong quai, fenugreek, feverfew, garlic, ginger, ginkgo, Panax ginseng, licorice , and others.

Many other drugs may affect the activity of warfarin.

Barbiturates, carbamazepine, rifampin, and hormonal contraceptives containing estrogen may ↓ the anticoagulant response to warfarin.Acute alcohol ingestion may ↑ action of warfarin.Chronic alcohol ingestion may ↓ action of warfarin if chronic alcohol abuse results in significant liver damage, action of warfarin may be ↑ due to ↓ production of clotting factor.

