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COUMADIN

Coumadin is a blood thinner. It is often prescribed by doctors for mature individuals to help them reduce the risk of heart disease and stroke. However, many supplements are also blood thinners. Fish oil especially at high doses appears also to be a blood thinner. So if you are taking enough fish oil, coumadin with unpleasant side effects may be unnecessary.

Dear Doc Roc: I take Coumadin, and am concerned about whether taking other supplements might interfere with its actions. -Patricia

Dear Patricia,
Coumadin, generic name Warfarin, is an anticoagulant. It is used to prevent blood clots from forming or growing in your blood and blood vessels. Anticoagulants are often callled blood thinners. The anticoagulant Coumadin increases the INR, a number that indicates to a doctor how fast your blood clots.  When you take a blood thinner, your INR goes up. Normal values are 2-3.  Blood thinners are prescribed on a long-term basis to patients who have experienced recurrent inappropriate blood clotting. This includes those who have had heart attacks, strokes, and deep vein thrombosis.
            However, many nutraceuticals also "thin the blood" by acting as anticoagulants. These include vitamin C, vitamin E, green tea, and fish oil. Doctors ought to check carefully which supplements their patients use. Which supplements interact with Coumadin is complicated, because different blood thinners work by different mechanisms. Most doctors simply advise patients not to take supplements – even though those vitamins may be very important for long term health and reduce the need for Coumadin. 
            Below is a table, based on the references below published in peer-reviewed professional journals.

Known to interact with warfarin-adjust Coumadin dosage: garlic, glucosamine with chondroitin, fish oil (please see additional esssay), ginko, ginseng, green tea, bilberry, licorice, niacin therapy (50 mg twice-a-day) had effects on INR parameters similar but not equal to Coumadin (4). Fish oil at 1-2 g/day increased INR from 2.8 to 4.3 within one month (5). Cranberry (300-400mg) twice a day increased INR, and can cause unstable INR and decreased INR also (5). Green tea at 250-500 mg contains significant quantities of vit K and decreased INR from 3.2 to 1.37.

Not known to interact with warfarin: primrose oil, Echinacea, calcium, zinc. Antioxidant therapy (800IU vitamin E, 1 g vitamin C, and 25 mg b-carotene) did not have a significant effect on coagulation parameters (4).  Vitamin C is not known to interact with warfarin, but vitamin E is (1).

When I receive reference 2, I will give more details about the interaction of fishoil and Coumadin.  Check back soon to get the rest of the story.

            Please send me your questions at ordman@beloit.edu, Subject: Nutrition Question, and I’ll answer the most intriguing ones in this column.  Remember – you are what you eat! Till next time ********Doc Roc
(1) Complimentary and alternative medicine use among patients starting warfarin, Brit. J. Haematol. 130:777-780 (2005)
(2) Fish oil interaction with warfarin, Buckley, M.S. et al, Annals of Pharmacotherapy 38:50-52 (2004)
(3) Inhibition of warfarin anticoagulation associated with chelation therapy, Grebe, H.B., et al, Pharmacotherapy 22:1067-1069 (2002)
(4) Effect of niacin, warfarin, and antioxidant therapy on coagulation parameters in patients with peripheral arterial disease in the Arterial Disease Multiple Intervention Trial, Carolyn M. Chesney, et al, Am Heart J 140: 631-6 (2000)
(5) Dietary Supplement and Selected Food Interactions with Warfarin, Noelle E. Daugherty et al, Pharmacology Update 29: 309-14 (2006)

INTERACTIONS OF COUMADIN AND FISH OIL

By Dr. Roc Ordman, PhD

Dear Patricia,
I hope you remember my letter on coumadin and supplements. I have examined the interaction of fish oil and Coumadin in particular, and received this evaulation from the Editor of the Natural Medicines Comprehensive Database, Philip J. Gregory, PharmD.

"The following paper suggests that the antiplatelet activity of 10 grams
of fish oil is less than aspirin: Svaneborg N, Kristensen SD, Hansen LM, et al. The acute and short-time
effect of supplementation with the combination of n-3 fatty acids and
acetylsalicylic acid on platelet function and plasma lipids. Thromb Res
2002;105:311-6. The following suggests that fish oil does NOT significantly affect INR
in warfarin treated patients: Bender NK, Kraynak MA, Chiquette E, et al. Effects of marine fish oils
on the anticoagulation status of patients receiving chronic warfarin
therapy. J Thromb Thrombolysis 1998;5:257-61

Our publication, Natural Medicines Comprehensive Database, has evaluated
this evidence in depth and makes the following statement regarding this
interaction: ANTICOAGULANT/ANTIPLATELET DRUGS <<interacts with>> FISH OIL
Interaction Rating = Minor (Be watchful with this combination)
Severity = Moderate * Occurrence = Unlikely * Level of Evidence = B

High doses of fish oils have antiplatelet effects. But fish oils might
not be as potent as aspirin in inhibiting platelet function.
Theoretically, concomitant use of fish oil with anticoagulant or
antiplatelet drugs may increase the risk of bleeding
(8671,8679,8696,11343,13769). However, conflicting research suggests
that taking fish oils 3-6 grams/day does not significantly affect INR
when use in patients taking warfarin (8801). Other research suggests
fish oils do not have additive antiplatelet effects when combined with
aspirin (13769). Monitor patients taking fish oils and drugs that affect
bleeding. Some of these drugs include aspirin, clopidogrel (Plavix),
dalteparin (Fragmin), dipyridamole (Persantine), enoxaparin (Lovenox),
heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.
You'll note that we rate this as a MINOR or likely insignificant
potential interaction."

Doc Roc: However, I recently received reference 1 below, read it carefully, and want to send this followup note to show the details of one study. The study describes how the coagulation property (measured as INR) of a 67 year old Caucasian woman's blood changed over 5 months as the woman took fish oil. Some supplements the woman was taking included 400 IU vitamin E and 81 mg aspirin. The goal for INR was to get a number between 2.0 and 3.0. During the first 2 months, the Coumadin dosage was adjusted to 1-1.5 mg per day, and remained at that level throughout the study.

So in this study, taking 1,000 mg of fish oil per day did not affect the INR and did not have a hazardous interaction with Coumadin. But taking 2,000 mg of fish oil per day did significantly increase the INR.

Based on this data, it would be wise for people of any age to discuss with your health professional take fish oil regularly when healthy because it has so many benefits. But if you start taking Coumadin, this study indicates that taking 1,000 mg of fish oil per day consistently is worthwhile in consultation with your health professional. The article below can be obtained from a good medical library or online, though the full article must be purchased .

            Please send me your questions at ordman@beloit.edu, Subject: Nutrition Question, and I’ll answer the most intriguing ones in this column.  Remember – you are what you eat! Till next time ********Doc Roc

(1) Fish oil interaction with warfarin, Buckley, M.S. et al, Annals of Pharmacotherapy 38:50-52 (2004) -http://www.theannals.com/cgi/content/abstract/38/1/50