A review of the oral direct thrombin inhibitor ximelagatran: not yet the end of the warfarin era...

Ximelagatran is a direct thrombin inhibitor that offers numerous potential advantages compared with traditional anticoagulants. It is given orally, has a rapid onset of action, does not require laboratory monitoring, and is not associated with immune-mediated thrombocytopenia. Numerous phase III trials with ximelagatran focusing on deep vein thrombosis prophylaxis and treatment, stroke prevention in patients with atrial fibrillation, and secondary prevention after acute myocardial infarction have been conducted. Results of these trials indicate that ximelagatran has similar efficacy and risk of bleeding compared with currently used anticoagulants. Accordingly, the potential of this agent to replace warfarin therapy for a variety of indications has been widely touted. Ximelagatran has already been approved in Europe for prophylaxis of venous thromboembolism in patients undergoing hip or knee surgery. However, an adverse effect of ximelagatran is liver enzyme elevation, which has been observed in 5% to 10% of patients with chronic administration of the drug. Although initially felt to be transient in nature, subsequent data presented to the Federal Drug Administration suggest a small but real risk of significant hepatotoxicity. These data led the advisory committee to the Federal Drug Administration to recommend against immediate approval of ximelagatran pending further information. The consistent results of completed trials with ximelagatran suggest that it has the potential to be used in many conditions that currently require treatment with warfarin and heparin products. The potential benefit that may be achieved by the replacement of these historically problematic narrow therapeutic index agents must be weighed against as yet undetermined long-term risks of hepatotoxicity.