Natural Health Research

Naturopathic Medicine
Health Quizzes
Warfarin, Coumadin


Warfarin is an anticoagulant medication used for the prophylaxis of thrombosis and embolism. Warfarin decreases blood coagulation by interfering with vitamin K metabolism.

Warfarin is a synthetic derivative of coumarin, a chemical found naturally in many plants, notably woodruff (Galium odoratum, Rubiaceae), and at lower levels in licorice, lavender and various other species. Warfarin was originally developed as a rat poison.


anticoagulant, vitamin K antagonist


antiphospholipid antibody syndrome, arterial thromboembolism prophylaxis, atrial fibrillation, deep venous thrombosis (DVT), deep venous thrombosis (DVT) prophylaxis, dilated cardiomyopathy, myocardial infarction prophylaxis, post-myocardial infarction, prosthetic heart valves, pulmonary embolism, stroke prophylaxis, unstable angina,

Side Effects

agranulocytosis, alopecia, anorexia, bleeding, chondrodysplasia punctata, cleft palate, diarrhea, exfoliative dermatitis, fetal abortion, intracranial hemorrhage, intraocular hemorrhage, leukopenia, nausea/vomiting, pruritus, purple-toe syndrome, skin necrosis, urticaria,

Drug-Vitamin-Herb Interactions

Negative interactions:

Blood thinners: DevilÕs claw, Dong Quai, Feverfew, Garlic, Ginger, Ginkgo, White willow, Chamomile, Coleus, Ginger, Horse chestnut, Red clover, Reishi
Natural blood thinners increase the risk of bleeding. Monitor PT and INR regularly.

Blood thinners: Vitamins A and E, Policosanol, Papaya, fish oil, GAGs, OPCs, phosphatidylserine
Natural blood thinners increase the risk of bleeding. Monitor PT and INR regularly.

Alfalfa and Green tea
Alfalfa and Green tea contain vitamin K.

Asian ginseng (Panax)
Asian ginseng may decrease effectiveness of Warfarin (one care report).

Coenzyme Q10
Coenzyme Q10 similar in structure to vitamin K, and may interfere with Warfarin (three case reports)

Danshen may increase effects of Warfarin, although it is not a blood-thinner

Ipriflavone may interfere with the normal breakdown of Warfarin, increasing risk of bleeding.

Papain and Bromelain
Papain and Bromelain may increase the risk of abnormal bleeding.

St JohnÕs Wort
St JohnÕs Wort may interfere with Warfarin.

Vinpocetine may interfere with Warfarin, although the effect is minor.

Vitamin K
Vitamin K antidotes effects of Warfarin




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