Substances That Conflict With Coumadin

Substances That Conflict With Coumadin

Coumadin is the brand name for warfarin, an anticoagulant. It works by blocking vitamin K, necessary for normal blood clotting - "thinning" the blood and preventing the formation of clots. This medicine is used to treat people who have had a deep vein thrombosis or pulmonary embolism. It is also used in those who have atrial fibrillation or a mechanical heart valve. Many medications, herbs, supplements and foods can interact with Coumadin and make its effects stronger or weaker.

Substances that can increase the effects of Coumadin

Coumadin binds to albumin, a type of protein naturally present in the blood. The amount that is not connected is the one that is active or "free". When you take other medications or consume other substances that bind to albumin, they can displace warfarin from albumin and increase the amount that is free or active. This means that the same amount of Coumadin has a greater effect. If Coumadin levels are very high in the blood, there is a risk of bleeding. Bleeding can happen anywhere, and it is potentially deadly. Coumadin is metabolized or broken down by the liver through a path used by many other types of drugs. The use of other drugs that use the same route as Coumadin is another way in which the level of Coumadin in the blood can rise too high. This also puts you at risk of bleeding. Certain common medications and other substances that can increase the level of Coumadin in the blood include NSAIDs, such as ibuprofen, naproxen, celecoxib, or acetaminophen, oral steroids, medications used to treat heartburn; certain antibiotics, antifungals, most statins - medications used to treat high cholesterol, some antidepressants, omega-3 fatty acids, green tea, and certain herbs, including St. John's wort, fenugreek, and Ginkgo biloba.

Substances that can interfere with the effects of Coumadin

Foods that contain vitamin K lower Coumadin levels. These are green leafy vegetables, such as kale, spinach, broccoli, Brussels sprouts, mustard greens and lettuce. Certain medications and other substances can also lower Coumadin levels, including thyroid medications, birth control pills, certain antibiotics, American ginseng, and coenzyme Q10. Decreasing levels of active Coumadin can put you at a higher risk of clotting.


If you take Coumadin, you may have other medical problems that require you to be taking some of these medications.That's fine, as long as your blood levels are being inspected, and the Coumadin dose is adjusted as needed. It is also good to eat as many servings of green leafy vegetables as you want, as long as you have your dose increasing to match the extra amount of vitamin K you are taking. Maintain a steady diet so that you take the same amount of vitamin K each day. Tell your doctor if you start taking new medications or have any changes in your diet.

Video Tutorial: Coumadin (Warfarin): Clinical Pharmacist Explains Everything You Should Know.

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