Abstract
Warfarin, an oral vitamin K antagonist, is used to prevent arterial and venous thromboembolism in patients suffering from a multitude of diseases. In 2004, 31 million warfarin prescriptions were dispensed in the United States. Warfarin inhibits the activation of the vitamin K-dependent clotting factors (Factors II, VII, IX, and X) and regulatory proteins (proteins C, S, and Z). It is one of the leading drugs implicated in emergency room visits for adverse drug reactions. Annually the frequency of bleeding complications associated with overanticoagulation is 15% to 20%, with fatal bleeds measuring as high as 1% to 3%. The most effective method of warfarin reversal involves the use of Four Factor Prothrombin Complex Concentrate (PCC), which is widely used throughout Europe but is unavailable in the United States. The current therapies available to emergency room physicians in the United States are fresh frozen plasma, recombinant Factor VIIa (rFVIIa), Factor Eight Inhibitory Bypassing Activity, or Three Factor PCC concomitantly administered with vitamin K. We review the advantages and disadvantages of these therapies and recommend Three Factor PCC with small doses of rFVIIa and with vitamin K in life-threatening situations if Four Factor PCC is unavailable.