Anticoagulant drugs reduce the risk of venous thromboembolic events after total 
hip and knee arthroplasty. However, the use of current drugs, such as low 
molecular weight heparins, is hampered by their subcutaneous route of 
administration. The use of vitamin K antagonists is hampered by the requirement 
for routine coagulation monitoring and dose titration to provide effective 
anticoagulation without an increased risk of bleeding and numerous food and drug 
interactions. Clearly, there is a need for new oral, fixed-dose anticoagulant 
drugs that do not require coagulation monitoring, while demonstrating similar or 
better efficacy and safety profiles when compared with current agents.