[New developments in anticoagulation with heparin; a short review.]

Low molecular-weight heparins (LMWH) are derivatives of standard unfractionated heparin (UFH) and both types of heparins are used for anticoagulation. UFH is heterogeneous with respect to molecular size and exerts its effect through enhancement of antithrombin III inhibition of serine proteases. Full dose UFH has a narrow therapeutic window as well as a short half-life and this mandates constant monitoring of its anticoagulatory effect. Weight-based dosing guidelines for unfractionated heparin have been shown to be safe and improve results. New modified heparins have lower molecular weight (LMWH) than UFH. The LMWH are dosed according to body weight without a need for monitoring tests and subcutaneous administration no more than twice daily is adequate. In studies comparing LMWH to UFH, the LMWH seem to be at least as effective as unfractionated heparin in preventing or treating venous thromboembolism. To date the comparison in these studies has been between LMWH and UFH dosed in the traditional way but a comparison of LMWH with UFH dosed by weight-based guidelines has not been studied yet.