|Clinical Development Phases I-III Regulatory, Quality, Manufacturing|
Treatment with new oral anticoagulant drugs does not require laboratory monitoring. However, there are some clinical settings where the measurement of the anticoagulant activity can be useful, especially in urgent surgery or invasive procedure. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are prolonged with good correlation with plasma drug concentration. The influence of rivaroxaban on PT is greater than that on aPTT, in contrast to dabigatran. Apixaban responses to PT and aPTT are weak. These tests are not specific and cannot detect low plasma concentrations. For direct Factor-Xa inhibitors, the most appropriate test is a modified anti-Xa chromogenic assay. A specific test unresponsive to heparins and fondaparinux has been developed. For dabigatran measurement, a modified thrombin clotting time, “Hemoclot,” has been well documented. The use of plasma calibrators allows an expression of the results in ng/ml of plasma. Expected peak concentration (2 to 4 h after drug intake) and trough concentration or Cmin—before a repeated administration—have been determined. More clinical work is warranted to determine possible adjustments of the drug according to its plasma concentration. Finally, the potential advantage of a punctual screening during long-term treatment has not been investigated.