Evaluation of the Antithrombotic Effects of Rivaroxaban and Apixaban Using the Total Thrombus-Formation Analysis System®: In Vitro and Ex Vivo Studies

BACKGROUND The usefulness of the Total Thrombus-Formation Analysis System® (T-TAS®) for monitoring the anticoagulant effects of non-vitamin K oral anticoagulants (NOACs) in clinical practice has been poorly addressed. METHODS NOACs (rivaroxaban and apixaban) were added to whole blood from healthy subjects in an in vitro study, and their effects on thrombus formation were evaluated by the T-TAS®. We also evaluated antithrombotic effects using ex vivo samples of whole blood from patients given rivaroxaban or apixaban at the respective trough and peak drug concentrations. RESULTS T-TAS® could determine anticoagulant effects in whole blood treated with rivaroxaban or apixaban in vitro. The increases in the anticoagulant effects of rivaroxaban and apixaban from the trough to peak concentrations in whole blood were successfully monitored by the T-TAS® using ex vivo samples. The antithrombotic effects of rivaroxaban and apixaban (in terms of factor Xa inhibition) at the peak were strongly linked to those at the trough. CONCLUSION T-TAS® could be a clinically useful tool for monitoring the anticoagulant effects of factor Xa inhibitors, and may represent an accurate quantitative analysis.