Comparison of rivaroxaban concentrations between Asians and Caucasians and their correlation with PT/INR
The objectives of this study are to compare steady-state trough (Cmin,ss) and peak (Cmax,ss) concentrations of rivaroxaban between Asians and Caucasians and to evaluate the relationship between rivaroxaban concentrations and prothrombin time/international normalized ratio (PT/INR). Recruited patients were advised on the time to take rivaroxaban. Cmin,ss and PT/INR were taken when patients arrived. Cmax,ss and PT/INR were drawn between 2 and 4 h later after the patient took rivaroxaban with food. Thirty patients were included in the analyses: 57% (n = 17) males and 43% (n = 13) females, 77% (n = 23) on 20 mg and 23% (n = 7) on 15 mg. Median PTtrough and PTpeak are moderately correlated with Cmin,ss (r2 = 0.43) and Cmax,ss (r2 = 0.49), respectively. Patients on 15 mg have lower Cmin,ss and Cmax,ss versus Caucasians [12 ng/ml vs. 57 ng/ml (Cmin,ss); 87 ng/ml vs. 229 ng/ml (Cmax,ss), p < 0.01 for both]. Patients on 20 mg also have lower Cmin,ss and Cmax,ss versus Caucasians [14 ng/ml vs. 44 ng/ml (Cmin,ss); 101 ng/ml vs. 249 ng/ml (Cmax,ss), p < 0.01 for both]. Subgroup analysis shows patients with BMI ≥ 30 have lower Cmax,ss than patients with BMI < 30 [80.47 ng/ml vs. 124 (p = 0.014)]. Cmin,ss and Cmax,ss were lower in Singaporeans than Caucasians. This may have an impact on the effectiveness of rivaroxaban in Singaporeans. Patients with higher BMI may not benefit similarly as patients with lower BMI. Lastly, the Dade Innovin reagent’s measure of PT/INR is not sensitive towards changes in rivaroxaban concentrations.
KeywordsRivaroxaban Plasma concentration PT INR Asian
Dr. Wang Jiexun for her help with the statistics. Dr. Ong Hean Yee, Dr. Lee Chee Wan, Dr. Ling Lee Fong, Dr. Leow Khang Leng, Dr. Dinna Soon Kar Nee, Dr. Michael Liang Mao Chen, Dr. Syed Saqib Imran, Dr. Justin Tang I-Shing, Dr. Cliff Wong Chun Pong, Dr. Ramkumar Sekar for letting us recruit your patients. Ms. Soh Lay See for extending a hand to help us with the logistics of the study.
This study was funded by National Medical Research Council (NRMC) Centre Grant Pitch-For-Fund. Award No: PFF15001.
Compliance with ethical standards
Conflict of interest
All authors declare no conflict of interest.
This study was approved by the Domain Specific Review Board (DSRB) prior to the commencement of the study (DSRB approval reference number: 2016/00195).
Informed consent was obtained from all individual participants included in the study.
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