Vitamin K Antagonist, Warfarin, Warfarin Therapy

Vitamin K Antagonist

Vitamin K is essential for the hepatic synthesis of Factors II (prothrombin), VII, IX, and X, as well as protein C and protein S.89, 93 Antagonists of vitamin K have been used as anticoagulants for over 50 years.
The most widely used medications for treating thrombosis are heparins and vitamin K antagonists (VKAs). These medications have proven efficacy, but lack many properties of an ideal anticoagulant.
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Warfarin

Warfarin, a synthetic derivative of coumarin, is the most commonly used vitamin K antagonist (VKA) in the United States. In some European countries, other coumarin derivatives (phenprocoumon and acenocoumarol) are used as an alternative to warfarin.7, 94
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Warfarin Therapy

Treatment with warfarin for four weeks to twelve months has been shown to reduce the risk of DVT recurrence by 90%. One exception to this general approach is the cancer patient with DVT, in whom long-term treatment (or therapy) with warfarin is less effective in preventing recurrence. LMWH, shown in one study to be roughly twice as effective in preventing this outcome, should be considered in these patients.120
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See also: Apixaban
See also: DVT Symptom
  • 89 - Haas S. New oral Xa and IIa inhibitors: updates on clinical trial results. J Thromb Thrombolysis. 2008;25(1):52-60.
  • 93 - Hirsh J, Dalen J, Anderson DR, et al. Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest. 2001;119(1 suppl):8S-21S.
  • 7 - Tran H, Ginsberg J. Anticoagulant therapy for major arterial and venous thromboembolism. In: Colman RW, Clowes AW, George JN, Goldhaber SZ, Marder VJ, eds. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 5th ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2006:1673-1688.
  • 94 - Verstraete M, Prentice CR, Samama M, Verhaeghe R. A European view on the North American fifth consensus on antithrombotic therapy. Chest. 2000;117(6):1755-1770.
  • 120 - Lee AY, Levine MN, Baker RI, et al;.Randomized Comparison of Low-Molecular-Weight Heparin versus Oral Anticoagulant Therapy for the Prevention of Recurrent Venous Thromboembolism in Patients with Cancer (CLOT) Investigators. Low-molecular-weight heparin versus a coumarin for the prevention of recurrent venous thromboembolism in patients with cancer. N Engl J Med. 2003;349(2):146-153.