SAMMC Departments: Coumadin - Mechanisms of Coumadin® Actions

Patient Information

Coumadin

Mechanisms of Coumadin® Actions

Coumadin® is an anticoagulant drug. It is only available by prescription, and should only be taken under the supervision of a physician familiar with its indications and actions. Coumadin® is based on a chemical known as warfarin sodium. Warfarin causes its anti-clotting effect by impairing the production of certain blood clotting proteins by the liver.

Administration of warfarin sodium blocks the action of vitamin K within the liver. The drug effectively competes for the same absorption sites within the liver needed for vitamin K uptake. Thus the levels of vitamin K within the liver decrease. Reduced amounts of clotting factors VII, IX, X, and II are produced, and the clotting action of the blood is progressively impaired. All of the actions of Coumadin® are due to the drug's inhibition of vitamin K. Thus, ingestion or administration of vitamin K can reverse the effects of Coumadin®. In fact, clinical overdosage with Coumadin® is corrected with vitamin K.

Dietary intake of vitamin K does affect the metabolism of Coumadin®. This is one of the reasons that each patient seems to require a different dose of the drug to reach the target anticoagulation effect. Each person has different dietary intake of vitamin K, and also different liver function, different excretion of the drug, etc. Thus it is important for the physician to monitor Coumadin® effect on the patients clotting mechanism. Without a monitor, patients would frequently be overdosed or underdoses, with potentially hazardous consequences.

Monitoring of the Coumadin® effect is performed with a blood test. This test is known as the INR or International Normalization Ratio. It is important that you review the INR information in The Coumadin® Clinic and become familiar with the routine used to monitor this drugs effect.

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Coumadin Information

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