Monitoring of Rivaroxaban in Patients with Atrial Fibrillation

[Speaker] Yuki Ohta:1
[Co-author] Makoto Takano:2, Tsukasa Kobayashi:1, Yuko Takeba:1, Masanori Ootaki:1, Minoru Watanabe:3, Yuki Nakamura:1, Taroh Iiri:1, Yoshihiro Akashi:2, Naoki Matsumoto:1
1:Department of Pharmacology, St. Marianna University School of Medicine, Japan, 2:Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, Japan, 3:Institute for Animal Experimentation, St. Marianna University Graduate School of Medicine, Japan

Background: Direct oral anticoagulants (DOACs) including rivaroxaban are use worldwide today. They have been developed aiming for easy-for-use drugs, those will not require laboratory monitoring, and having less drug-drug interaction. Although having those aim in development, the assessment of the anticoagulation effect of DOACs may be necessary in routine clinical circumstances not only in emergency. It is reported that the prothrombin time (PT) shows correlation with the blood concentration of rivaroxaban, but some PT test kits are said to correlate less due to their lower sensitivity. Therefore, the activated partial thromboplastin time (APTT) is used for its assessment in our hospital. In this study, we examined the correlation between anti-factor Xa (FXa) activity and APTT in atrial fibrillation patients taking rivaroxaban.
Methods: Twenty-three patients with AF received a single 10 or 15 mg dose of rivaroxaban daily were enrolled after informed consent. Anti-FXa activity, PT, and APTT were measured twice on the separate days at least 8 weeks.
Results: The characteristics of subjects are following: age, CHADS2 score, and CHA2DS2-VASC score, 74.5 ± 9.2 y, 1.8 ± 1.0, and 3.2 ± 1.3, respectively. The correlation coefficients of PT (%) or APTT (sec) for anti-FXa were 0.50 and 0.60, respectively. There were somewhat correlation between both. The correlation for APTT was stronger than for PT.
Conclusion: Anti-FXa activity is considered to reflect the concentrations of rivaroxaban, that is not routinely measured in hospital laboratories although it is highly reliable. Our results showed that so-called "poorly respond" PT test kit may suggest anti-FXa activity, and APTT may have better potential than those "poorly respond" PT kit.
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