 The major adverse event associated with anticoagulant and antithrombotic drugs is bleeding, which can cause permanent disability and death Ebbesen et al., 2001; Levine et al., 2004. Generally, cardiovascular clinicians have been willing to trade off an increased risk of bleeding when a drug can reduce the ischemic complications of either the acute coronary syndromes or of coronary revascularization procedures. However, recent data have suggested that bleeding events, particularly those that require blood transfusion, have a significant impact on the outcome and cost of treatment of patients with ACS. Transfusion rates in patients undergoing elective coronary artery bypass graft CABG surgery range from 30-60, and transfusion in these patients is associated with increased short, medium and long-term mortality Bracey et al., 1999; Engoren et al., 2002; Hebert et al., 1999. Bleeding is also the most frequent and costly complication associated with percutaneous coronary interventions PCI, with transfusions being performed in 5-10 of patients at an incremental cost of 8000-12,000 Moscucci, 2002. In addition, the frequency of significant bleeding in patients undergoing treatment for ACS is high as well, ranging from 5 to 10 excluding patients who undergo CABG, with bleeding and transfusion independently associated with a significant increase in short-term mortality Moscucci et al., 2003; Rao et al., 2004. Therefore, despite the continued development of novel antithrombotics, a significant clinical need exists for safer anticoagulant agents. 