[New anticoagulant drugs for atrial fibrillation. Feasibility and necessity of monitoring].

Two novel oral anticoagulants, namely the direct thrombin inhibitor dabigatran and the direct factor Xa inhibitor rivaroxaban, have recently been approved for treatment of atrial fibrillation. They differ in many ways from vitamin K antagonists, including rapid onset of action, shorter half-life, fewer drug-drug interactions, lack of a need for monitoring and no need for titration or dose adjustments. Commonly available global coagulation time assessments (e.g. prothrombin time and activated partial thromboplastin time) are highly influenced by rivaroxaban and dabigatran but these assays are relatively insensitive. Ideally these anticoagulant agents would be assessable using a sensitive and standardized test with a linear dose-response curve. Optimized assays are currently under investigation and may quantify the anticoagulant effect. At present the therapeutic ranges for dose adjustment have not yet been established.