Pentasaccharides in the prophylaxis and treatment of venous thromboembolism: a systematic review.

PURPOSE OF REVIEW: The aim of this review is to perform a critical analysis of all completed studies evaluating pentasaccharides-synthetically derived, selective inhibitors of activated factor X-in prophylaxis in major orthopedic surgery and the treatment of venous thromboembolism.

RECENT FINDINGS: Venous thromboembolism is a disorder with considerable morbidity when left untreated. New antithrombotic agents have been developed that selectively inhibit components of the coagulation system, thereby avoiding the difficulties associated with current anticoagulants. The pentasaccharides fondaparinux and idraparinux are the first of a new class of synthetic selective inhibitors of activated factor X. Fondaparinux has been extensively investigated in two areas: orthopedic surgery and venous thromboembolism. It is clear from four thromboprophylaxis studies in major orthopedic surgery that fondaparinux is 50% more effective in reducing venous thromboembolism than enoxaparin. This superior efficacy led to an overall increase in major bleeding, which was however primarily due to more fondaparinux-treated patients with bleeding indexes of 2 or greater. The incidence of fatal bleeding, critical organ bleeding, or bleeding leading to reoperation did not differ significantly between the two groups. In the initial treatment of patients with proximal vein thrombosis and pulmonary embolism, fondaparinux was equally effective as low molecular weight heparins and unfractionated heparin, respectively, without a different incidence in major bleeding in fondaparinux and comparator heparin groups.

SUMMARY: Fondaparinux, one of the first of a new class of synthetic selective factor Xa inhibitors, is overall 50% more effective in reducing venous thromboembolism than enoxaparin in major orthopedic surgery, with an overall 1% increased rate of major bleeding, when compared with enoxaparin. The incidence of fatal bleeding, critical organ bleeding, or bleeding leading to reoperation did not differ significantly between the two treatment groups. Fondaparinux is equally effective as low molecular weight heparins and unfractionated heparin in the initial treatment of patients with proximal vein thrombosis and pulmonary embolism, respectively. Finally, as with any new drug, fondaparinux should be used cautiously and only in patients who reflect the population of the clinical trials in which the drug was evaluated.