Drug trials that have influenced our practice in the treatment of venous thromboembolism.

Heparin and oral anticoagulants have been the mainstay of antithrombotic therapy for the prevention and treatment of venous thromboembolism for over 50 years. Randomized trials have established their efficacy and have been used to refine the optimal dose and duration of therapy for different indications. Low-dose, subcutaneous, standard heparin and low molecular weight heparin (LMWH) provide effective primary prophylaxis, higher doses being indicated for patients who are at highest risk. OA is an alternative in high risk patients, particularly if there are persistent risk factors. Heparin and OA can be started concomitantly when treating patients with acute VTE. At least 4 days of adjusted dose standard heparin, or fixed dose LMWH, should be administered, and heparin should not be stopped until therapeutic OA is established. Acute DVT can be treated as an outpatient with fixed dose LMWH. In general, OA, with an International Normalization Ratio of 2.0-3.0, should be continued for 3 to 6 months. The optimal duration of OA may differ between patients who have VTE associated with a transient or a continuing (including "idiopathic") risk factors; however, this remains to be defined. New antithrombotic agents, such as direct thrombin inhibitors, are in the preliminary stages of evaluation for the prevention and treatment of VTE.