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Coumadin and conflicts with alternative therapy


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My cancer kicks out blood clots so I need to be careful of my INR levels. While researching CoQ10, I noticed that it could interfer with Coumadin (Warfarin).

I copied the following, then lost the link and can't find the website again. I'll just post the whole thing - sorry. (Credit for the original research is given at the bottom.)

July 1, 2000 - Probably one third of adults in the United States use alternative therapies, including herbs. In 1997, herbal medicine sales reached $3.24 billion. A concern is possible interactions between these alternative products and prescription drugs. More food and drug interactions have been reported for Coumadin (warfarin) than for any other prescription drug. Such interactions may lead to bleeding episodes or stroke by increasing or reducing Coumadin's effect. Herbal products that may change Coumadin's effect include:

angelica root

arnica flower




borage seed oil


capsicum chamomile




horse chestnut

licorice root

lovage root

meadowsweet passionflower herb



red clover


sweet clover


willow bark

Actual documented reports claim interactions with Coumadin, including:

Coenzyme Q10


devil's claw dong quai


green tea papain

vitamin E

Some natural substances have blood-thinning properties. Coumarins (coumadin-like substances), salicylates (aspirin-like substances) and anti-platelets (substances that prevent blood cells from clumping together) all are "blood thinning." A possible risk exists when taking such a product while also taking Coumadin. Herbs thought to contain blood-thinning substances include:

Contain coumarin Contain salicylates Anti-platelet

angelica root

arnica flower






horse chestnut

licorice root

lovage root


passionflower herb


red clover


sweet clover Meadowsweet


willow bark bromelain




There are no documented reports of a proven interaction between Coumadin and any of these herbs! However, patients taking these herbs while on Coumadin should be closely watched for signs of bleeding. Because of serious consequences in cattle, patients taking both sweet clover and Coumadin should be very closely monitored.

Feverfew (Tanacetum parthenium) is commonly used for treating migraine headaches, arthritis, and various allergies. Feverfew may reduce serotonin release, histamine release, and coagulation. Several lab studies have shown feverfew to interfere with coagulation. There are no documented reports of feverfew interacting with Coumadin in humans, but data suggest risk for a stronger blood thinning effect when taking both. For now, it is recommended that patients taking Coumadin avoid products containing feverfew.

Garlic (Allium sativum) is thought to have several cardiovascular benefits, such as blood pressure lowering, cholesterol lowering, and anti-stroke activity. Garlic oil has been reported to reduce coagulation. One author reported that cells were less likely to clump together (coagulate) in a lab setting when blood samples from healthy adults were mixed with essential garlic oil. There have been no documented reports of serious interaction effects when taking both Coumadin and garlic. However, the available information suggests that a serious interaction is possible. Patients taking Coumadin should avoid garlic supplements. Eating food containing small amounts of garlic should not be a problem.

Ginger (Zingiber officinale), taken for motion sickness and arthritis, has been reported to reduce blood clotting. Ginger supplements - which contain much higher amounts of ginger than food products - may increase risk of bleeding when taken with Coumadin. Patients taking both should have their INR checked regularly and watch for symptoms of bleeding.

Ginkgo (Ginkgo biloba) is a common herbal product advertised to improve mental function. Ginkgolide B, one component of ginkgo, reduces coagulation. Several cases of bleeding thought to be caused by ginkgo use have been reported. A 70 year old man took 40mg of concentrated ginkgo extract twice a day for one week. He complained of blurred vision and was diagnosed with a spontaneous hemorrhage in one eye. He was also taking 325mg aspirin daily. A second report involved a 33 year old woman who complained of headaches and was later diagnosed with bruises around her spine. She had taken 60mg of ginkgo twice a day for 2 years. Another report described a 72 year old woman diagnosed with a subdural bruise after taking 50mg of ginkgo 3 times a day for at least 6 months. There are no reports of bleeding caused by taking both Coumadin and ginkgo. However, it is recommended that patients taking Coumadin not take ginkgo-containing products.

Herbal products reported to interact with Coumadin include danshen, devil's claw, dong quai, green tea, ginseng, and papain. Nutrients such as CoQ10 and also vitamin E have been reported to affect blood thinner therapy. It should be noted that all this information is taken mainly from individual case reports so it is not too reliable.

Coenzyme Q10 is found in plant, animal, and human cells. It is involved in electron transport and may be a free-radical scavenger, an antioxidant, and a membrane stabilizer. CoQ10 is promoted to treat heart failure, high blood pressure and angina. Since CoQ10 is structurally similar to vitamin K 2, it may have blood-coagulating effects. The vitamin K-like effects of CoQ10 have been demonstrated in a lab setting and in 4 case reports. In Denmark, a 72 year old woman had a decreased response to Coumadin while she was taking CoQ10. Proper INR was achieved only when she stopped taking the product. A 68 year old man with a history of stroke who was stabilized with Coumadin for 6 years saw his INR drop after taking 30mg CoQ10 daily for 2 weeks. The other case reports involved a 72 year old man and a 70 year old woman who saw their INR go down within 2 weeks of starting CoQ10. Each of these patients returned to normal INR after stopping CoQ10. If CoQ10 and Coumadin are taken, patients should be monitored carefully for the first 2 weeks.

Danshen (the root of Salvia miltiorrhiza), also known as tan seng, is a very popular herb recommended in the Chinese community for heart disease. Danshen's effects include low blood pressure, making the heart beat more strongly, vasodilation, and reduced coagulation. Studies in rats show that danshen definitely alters the effects of Coumadin. There have been several case reports of Coumadin-danshen interaction. A 62 year old man who had been taking 5mg Coumadin daily after a mitral valve replacement and who had a stable INR for several weeks was admitted to a Hong Kong hospital with bleeding in lungs and heart. His INR was over 8.4. The man said he had taken a danshen extract daily for 2 weeks before his admission. A 66 year old man who had been taking 2.5mg Coumadin daily for nearly a year was hospitalized for internal bleeding. His INR was 5.5. He reported consuming danshen 3 and 5 days before admission. Both this man and another 48 year old woman achieved a proper INR after stopping danshen. Available evidence strongly discourages use of both Coumadin and danshen.

Devil's Claw (Harpagophytum procumbens) is an expensive herbal product that has been promoted as a pain reliever for arthritis, gout, and myalgia. Although information about devil's claw is limited, one case of rash-like skin bruising was reported in a patient taking both Coumadin and devil's claw. Until more is known about this possible interaction, patients taking Coumadin are advised to avoid devil's claw.

Dong quai (Angelica sinensis) is a Chinese herb promoted in the US for treating menopausal complaints and menstrual disorders. Dong quai contains at least 6 coumarin derivatives; these substances may promote vasodilation and have anti-inflammatory, antipyretic, antispasmodic, immunosuppressant, and estrogen-like effects. Dong quai may also reduce coagulation. A study in rabbits also suggests risk of increased PT times when this herb is taken with Coumadin. A recent case report supports this idea. A 46 year old woman who had been taking 5mg Coumadin a day for 2 years saw a sudden increase in her INR to 4.9. The patient denied any changes in routine except for adding 565mg dong quai once or twice a day during the previous 4 weeks for menopausal symptoms (her herbalist had recommended this). After 4 weeks off dong quai, her INR returned to normal. In light of this information, patients taking Coumadin are advised to avoid dong quai.

Ginseng Three ginseng species are claimed to enhance energy, reduce effects of stress, and improve mood - American ginseng (Panax quinquefolius), Oriental ginseng (Panax ginseng), and Siberian ginseng (Eleutherococcus senticosus). The active components of ginseng and their potency vary widely among ginseng products. This makes it difficult to study the safety of ginseng products. One published case report suggests that Oriental ginseng (Ginsana) may alter Coumadin's effect. The INR of a 47 year old man who had been taking Coumadin for 9 months for his mechanical heart valve began taking Oriental ginseng, and within 2 weeks his INR fell to 1.5. His INR returned to proper level 2 weeks after stopping ginseng. A 1999 study in rats did not show a significant interaction between Coumadin and pure ginseng extract. It is unknown whether patients taking Coumadin should avoid ginseng.

Green Tea (Camellia sinensis), also known as Chinese tea, is claimed to prevent cancers, treat stomach disorders, and improve mental function. Although dried green tea leaves contain substantial amounts of vitamin K, brewed green tea is not a significant source of the vitamin. However, large amounts of brewed green tea might alter Comadin's effects. The INR of a 44 year old patient with a mechanical heart valve went way down when he started drinking large amounts of brewed green tea. The patient reported to a clinic with an INR of 1.37; his INR 22 days earlier had been 3.79. The man said he had begun drinking ½ - 1 gallon of brewed green tea daily about a week before his INR dropped. A significant drop in INR would not usually be expected from drinking moderate amounts of brewed green tea.

Papain is a mixture of enzymes found in extract of papaya, the fruit of the papaya tree (Carica papaya). It is taken orally in the belief that it reduces edema, inflammation, diarrhea, and psoriasis. One case has been seen of a patient who had maintained proper INR on Coumadin, then began taking papaya extract containing papain as a weight-loss aid. The patient was admitted for heart surgery with an INR of 7.4. After withdrawal of both papaya extract and Coumadin, the patient's INR went down to 2. The details of the case have not been published. Patients on Coumadin should probably avoid papain for now

Vitamin E has received much publicity for treating heart disease. Vitamin E may slow oxidation of vitamin K. Vitamin K oxidation is necessary for blood to clot. Information about the effect of vitamin E on PT time varies. A 55 year old man on Coumadin and 1200 IU of vitamin E daily developed blood vessel ruptures under the skin, bloody urine, and high PT time. After re-stabilizing off vitamin E, he was given 800 IU of vitamin E again to see if that was the problem. The same problems reappeared. Within a week after stopping vitamin E again, his PT time went back down.

Humans consuming adequate vitamin K and not taking Coumadin have no unexpected bleeding problems. However, vitamin K-deficient animals show a tendency toward bleeding with vitamin E. A study in 12 patients on Coumadin who took 100 or 400 IU of vitamin E daily for one month found that neither dose caused bleeding. Kim and White did a randomized, double-blind study in which 4 patients took 1200 IU vitamin E daily, 3 patients took 800 IU daily, and 4 took placebo, all for 4 weeks. During the study's second phase, which was single-blind and not randomized, 6 subjects were told they would receive placebo or vitamin E, but all were given 1200 IU daily for another 4 weeks. Their INR did not increase to a point requiring Coumadin dose adjustment. Vitamin E up to 400 units per day does not seem to affect PT time in patients on Coumadin. Patients on Coumadin who begin taking vitamin E - especially dosages greater than 400 IU daily - should have INR measurements done 1 - 2 weeks after starting vitamin E. This should be followed by INR monitoring every 2 - 4 weeks during the first 2 months of combination therapy.

Limitations Nearly all available information on herb-Coumadin interactions is based on lab studies, animal studies, or individual case reports. Cause and effect relationships have not been proven. Available reports give limited information about the severity of these interactions. There is little reliable information about the safety and effectiveness of most herbal products. There are no regulations governing purity and potency of herbal products during manufacturing.

Note The FDA recently established the Special Nutritionals Adverse Event Monitoring System, a searchable database. This database includes reports that have been submitted to MedWatch and can be accessed at http://vm.cfsan.fda.gov/~dms/aems.html.

May increase bleeding risk Does increase bleeding risk May lessen Coumadin's effect

Angelica root

Arnica flower




Borage seed oil











Horse chestnut

Licorice root

Lovage root




Passionflower herb



Red clover


Sweet clover


Willow bark Danshen

Devil's claw

Dong quai


Vitamin E Coenzyme Q10


Title: Potential Interactions Between Alternative Therapies and Warfarin

Authors: Amy M. Heck, Beth A. Dewitt, and Anita L. Lukes

Source: Am J Health-Syst Pharm 57(13):1221-1227, 2000

All information on this site is opinion only. All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor. Use the reference information at the end of each article to search MedLine for more complete and accurate information. All original copyrights apply. No information on this page should be used by any person to affect their medical, legal, educational, social, or psychological treatment in any way. I am not a doctor. This web site and all its pages, graphics, and content copyright © 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Jon C.

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I have read that Lovenox ( low molecular weight heparin given by shot in the abdomen) is the best treatment for clots caused by cancer. As far as Warfarin ( Coumadin) any vegetable or food that contains Vitamin K will throw off your INR. Donna G

www.drugs.com/coumadin.html - 62k - Nov 8, 2004

http://www.thedoctorwillseeyounow.com/a ... cer/hep_4/

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Hi Donna G

Congratulations on your long term survival. Hope we can all do as well. Any hints on the significant events that have worked for you?

I took Lovenox when first diagnosed with blood clots and before/after having a port installed. The cheapest place I could find them was at Walmart for $68 per vial. Giving myself shots to the fatty area on my stomach twice each day was not fun! The shots left bruises on my stomach that took months to go away – later found out I should have tried to apply pressure to the area after the shot. Coumadin (Warfarin is generic) is easier, less painful and significantly cheaper – you just have to get your INR checked regularly and as you pointed out, watch what you eat or take.

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  • 1 month later...


I was on Coumadin for quite a while after having clots. I was allowed to take certain supplements that were known to affect INR with the provision that I would use them consistently and would have more frequent tests any time my diet or suppment usage changed. No one who uses coumadin has the same diet. That is why the blood is tested for each individual to determine the proper dose. If you keep your intake of vitamins a constant, it shouldn't be too hard to regulate your coumadin dosage. This would of course be with the knowlege and approval of your medical team as it was with mine at the time. Let us know how it goes. As an aside, my oncologist did ask me to cut out the supplements once I went on Iressa. I have done so although I do eat my way through an awful lot of antioxidents and vitamins. :wink:

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