Coumadin is the brand name for the generic drug warfarin. It is classified as an anticoagulant, a drug that inhibits blood clotting. It is prescribed for the prevention or treatment of blood clots associated with atrial fibrillation, artificial heart valves, heart attack and certain conditions that predispose to blood clots. Coumadin's mechanism of action is tied closely with vitamin K, and their interactions can be complex.
Coumadin
Coumadin works by impairing the normal metabolism of vitamin K. It blocks an enzyme that acts to "recycle" vitamin K within the body. It is prescribed in cases known to be at increased risk for blood clots. Such conditions as atrial fibrillation, an abnormal heart rhythm, artificial heart valves, cancer and some protein deficiencies predispose one to blood clots. Other disorders such as heart attack or deep venous thrombosis or DVT are often treated with Coumadin to prevent the progression of blood clots. While Coumadin can be life-saving, it may produce life-threatening bleeding complications if not closely regulated.
Vitamin K
Vitamin K is a fat-soluble vitamin essential for the normal function of several proteins involved in the blood clotting process. The Linus Pauling Institute notes that the body stores very little vitamin K, so a process exists whereby the vitamin is reused several times. Because of this, and the dietary availability of vitamin K, deficiency is uncommon. Similarly, vitamin K excess is rare, as that obtained through the diet is non-toxic.
Coumadin-Vitamin K interaction
Coumadin inhibits vitamin K's role in producing blood clotting factors. However, increased levels of vitamin K in the body can overcome this inhibition and reduce the effects of Coumadin. Sometimes this fact is used to an advantage. For example, if Coumadin activity is too high increasing the risk of bleeding, vitamin K can be administered orally or intravenously. This interaction is neither instantaneous nor entirely predictable and the whole situation best avoided if possible. This can be accomplished by close monitoring of the drug's effect on blood clotting through medical testing.
Dietary Considerations
Vitamin K is readily available through the diet. Leafy green vegetables are excellent food sources of the nutrient. The National Institutes of Health lists kale, spinach, Brussels sprouts, broccoli, lettuce and turnip and mustard greens as foods high in vitamin K. The most important factor in the Coumadin-vitamin K interaction is consistency in vitamin K intake. If the amount or frequency of vitamin K intake is variable, the dosing of Coumadin is challenging and potentially dangerous. However, a diet of consistent vitamin K levels allows for the adjustment of the Coumadin dose.
