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Mechanisms of Warfarin Actions
Warfarin 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. Warfarin 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 Warfarin are due to the drug's inhibition of Vitamin K. Thus, ingestion or administration of Vitamin K can reverse the effects of Warfarin. In fact, clinical overdosage with Warfarin is corrected with Vitamin K.
Dietary intake of Vitamin K does affect the metabolism of Warfarin. 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 Warfarin effect on the patients clotting mechanism. Without a monitor, patients would frequently be overdosed or underdoses, with potentially hazardous consequences.
Monitoring of the Warfarin 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 Anticoagulation Clinic and become familiar with the routine used to monitor this drugs effect.
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