Fondaparinux: a new antithrombotic agent

Venous thrombosis is usually triggered by a low-flow state, as in prolonged periods of bed rest after hip or knee surgery. Antithrombotic agents are the drugs of choice in such circumstances. The new factor Xa inhibitor fondaparinux has been approved by the US Food and Drug Administration for the prevention of venous thromboembolism in patients undergoing hip fracture surgery, hip replacement surgery, or knee replacement surgery.

The aim of this article was to review the clinical pharmacology of fondaparinux and summarize the data from available clinical trials of this agent.

The terms fondaparinux, SR90107A/ORG31540, and factor Xa were used to search MEDLINE and Current Contents/Clinical Medicine for English-language studies in humans published between 1996 and May 2002. Unpublished data were provided by the manufacturer of fondaparinux, and additional information was obtained from abstracts presented at the 2001 congress of the International Society on Thrombosis and Haemostasis in Paris.

Fondaparinux is a synthetic pentasaccharide that selectively binds to antithrombin III, inducing a conformational change that increases anti-factor Xa activity. Phase III studies to date have reported that fondaparinux had greater efficacy compared with enoxaparin in terms of prevention of venous thromboembolism after hip or knee replacement surgery. Preliminary studies have suggested that this agent may have efficacy in the treatment of deep vein thrombosis, as well as in the management of acute coronary syndromes. However, 1 study reported a significant increase in the risk of major bleeding with fondaparinux compared with enoxaparin (2.1% vs 0.2%, respectively; P = 0.006), and another reported a significant increase in the risk of minor bleeding (4.1% vs 2.1%; P = 0.02).

Fondaparinux has shown efficacy in the prevention of venous thromboembolism in patients undergoing hip or knee replacement surgery. Large-scale clinical trials of its potential efficacy in deep vein thrombosis and acute coronary syndromes are ongoing. Use of fondaparinux may be associated with an increased bleeding risk, and patients should be assessed individually to ensure that the possible benefits outweigh the risks. Routine use of fondaparinux as a replacement for low-molecular-weight heparin is not recommended at this time.