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AMBULATORY CARE

Duration of Anticoagulant Therapy After Initial Idiopathic Venous Thromboembolism

Pharmacotherapy Specialist, Internal Medicine, Akron General Medical Center, Akron, OH; Associate Professor of Clinical Pharmacology in Internal Medicine, Northeastern Ohio Universities College of Medicine, Rootstown, OH

Diane L Chomo, MD FACP

Associate Director, Internal Medicine Center of Akron, Akron; Associate Professor of Clinical Internal Medicine, Northeastern Ohio Universities College of Medicine

Reprints: Lawrence A Frazee PharmD, Akron General Medical Center, 400 Wabash Ave., Akron, OH 44307-2463, FAX 330/996-2395, lfrazee{at}agmc.org

OBJECTIVE: To review the literature investigating the duration of oral anticoagulant therapy following a first event of idiopathic venous thromboembolism (VTE).

DATA SOURCE: MEDLINE (1967-April 2003) and bibliographic searches of the English-language literature pertaining to the duration of oral anticoagulant therapy following a first event of idiopathic VTE was conducted. Search terms included venous thromboembolism, anticoagulation, duration of treatment, warfarin, and idiopathic.

STUDY SELECTION AND DATA EXTRACTION: The results of all trials and meta-analyses that were obtained are reviewed and critiqued.

DATA SYNTHESIS: The risk of recurrent VTE following a first idiopathic event is similar to the risk in patients with a permanent risk factor. Conventional-intensity oral anticoagulant therapy reduces this risk by 80-90%, but at an annual risk of bleeding of approximately 2-3%. According to the PREVENT trial, low-intensity anticoagulation also affords protection against VTE recurrence, but at a lower risk of bleeding. Older trials indicated that longer therapy was superior to shorter therapy; however, data from recent trials have demonstrated that the benefit was maintained only while receiving therapy.

CONCLUSIONS: Patients with a first episode of idiopathic proximal VTE should be considered for indefinite anticoagulant therapy. The appropriate intensity of anticoagulation is still controversial; however, it appears that low-intensity treatment would be appropriate in most patients. For patients who will not continue therapy indefinitely, there does not appear to be any long-term benefit to extending the duration of therapy from 3 to 6 months.

Key Words: anticoagulation, duration of therapy, idiopathic venous thromboembolism, warfarin

Published Online, August 29, 2003. www.theannals.com, DOI 10.1345/aph.1C486

THIS ARTICLE IS APPROVED FOR CONTINUING EDUCATION CREDIT
ACPE UNIVERSAL PROGRAM NUMBER: 407-000-03-031-H01