Therapy of Acute Thromboembolism with Heparin and Warfarin

Abstract

The indications, efficacy, dosage, administration, and monitoring of heparin and warfarin therapy for acute thromboembolic events are reviewed, with emphasis on recent changes in treatment recommendations. High-dose heparin therapy is indicated for acute deep-vein thrombosis and pulmonary embolism. Heparin therapy as an adjunct to thrombolytic agents for acute myocardial infarction is becoming increasingly accepted. Heparin therapy for acute thromboembolic events consists of a dosage that elevates the activated partial thromboplastin time to 1.5 to 2.0 times the control value; formerly, 1.5 to 2.5 times control was considered therapeutic. The recommended heparin dosage is a bolus dose of 70-100 units/kg followed by an infusion of 15-25 units/kg/hr. To prevent recurrent thromboembolism, most patients require long-term therapy following acute treatment; this typically consists of warfarin, which should be initiated on day 1 or 2 of heparin therapy whenever possible. For most indications, the intensity of warfarin has been reduced to a dosage that elevates the prothrombin time to 1.3 to 1.5 times control. Alternative therapies (low-molecular-weight heparins) and routes (subcutaneous heparin) should be further investigated. Current recommendations for heparin and warfarin therapy of acute thromboembolism include reduced intensity of both drugs and shortened duration of therapy. Since the therapeutic ranges for both heparin and warfarin therapy have been compressed, closer monitoring may be necessary to achieve and maintain adequate anticoagulation.