Thromboembolic disorders are among the major causes of morbidity and mortality, and anticoagulation remains the cornerstone of prevention and treatment of these disorders. Although effective, the well-established agents have significant drawbacks. Heparin, low molecular weight heparin, and fondaparinux must be given parenterally, which is inconvenient for long-term or home use. The orally administered vitamin K antagonists (such as warfarin) have a slow onset of action, thus requiring bridging therapy with a parenteral agent when immediate anticoagulation is needed (e.g. inpatients with acute deep vein thrombosis). Because vitamin K antagonists produce a variable anticoagulant response as a result of multiple drug-drug and food-drug interactions and genetic polymorphisms, frequent coagulation monitoring and dose adjustment are required to ensure a therapeutic level of anticoagulation, which is inconvenient for both patients and physicians. In the search for new agents to overcome the drawbacks associated with traditional agents, direct Factor Xa inhibitors (e.g. rivaroxaban, apixaban, and edoxaban) and direct thrombin inhibitors (e.g. dabigatran etexilate) have been developed and are undergoing late-stage clinical evaluation for the prevention and treatment of thromboembolic disorders. These new oral agents have already shown promise in large-scale clinical studies and data suggest that we have entered a new era with novel drugs that are closer than ever to the 'ideal anticoagulant'. Because these new oral agents have a rapid onset of action and can be given at fixed doses without the need for routine coagulation monitoring, they may simplify treatment paradigms and are expected to improve overall clinical outcome.
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