The Direct Oral Anticoagulants Apixaban, Rivaroxaban, and Edoxaban

Abstract

Traditionally, anticoagulant therapy has been conducted through the administration of vitamin K antagonists (VKAs) and parenteral alternatives. Direct Oral Anticoagulants (DOACs) such as apixaban, rivaroxaban and edoxaban provide the convenience of the VKA in that they are administered orally yet they lack many of the disadvantages associated with VKA therapy. Unlike VKAs, measuring DOAC levels is usually unnecessary. However, there are instances with plasma concentrations should be determined. The chromogenic anti-Xa assay is the best linear quantitative assay that is easily accessible to most clinical laboratories for this purpose. However, since the calibrators and controls for apixaban, rivaroxaban and edoxaban are awaiting Federal Drug Administration (FDA) clearance, measurement may have to be performed using the Prothrombin Time assay that lacks the sensitivity of the chromogenic anti-Xa. Results should be periodically verified using liquid chromatography in tandem with mass spectrometry which is the reference method for measuring DOAC levels in plasma. ABBREVIATIONS: AF-atrial fibrillation, DOAC – direct oral anticoagulant, DVT – deep vein thrombosis, FDA – Food and Drug Administration, HPLC – high performance liquid chromatography, LMWH – low molecular weight heparin, PE – pulmonary embolism, PT – prothrombin time, UFH – unfractionated heparin, UPLC – ultra-performance liquid chromatography, VKA – vitamin K antagonist, VTE – venous thromboembolism