Population Pharmacokinetics and Dose Optimization Based on Renal Function of Rivaroxaban in Thai Patients with Non-Valvular Atrial Fibrillation

Low-dose rivaroxaban has been used in Asian patients with direct oral anticoagulants (DOACs) eligible for atrial fibrillation (AF). However, there are few pharmacokinetic (PK) data in Thai patients to support precise dosing. This study aimed to develop a population PK model and determine the optimal rivaroxaban doses in Thai patients. A total of 240 Anti-Xa levels of rivaroxaban from 60 Thai patients were analyzed. A population PK model was established using the nonlinear mixed-effect modeling approach. Monte Carlo simulations were used to predict drug exposures at a steady state for various dosages. Proportions of patients having rivaroxaban exposure within typical exposure ranges were determined. A one-compartment model with first-order absorption best described the data. Creatinine clearance (CrCl) and body weight significantly affected CL/F and V/F, respectively. Regardless of body weight, a higher proportion of patients with CrCl < 50 mL/min receiving the 10-mg once-daily dose had rivaroxaban exposures within the typical exposure ranges. In contrast, a higher proportion of patients with CrCl ≥ 50 mL/min receiving the 15-mg once-daily dose had rivaroxaban exposures within the typical exposure ranges. The study’s findings suggested that low-dose rivaroxaban would be better suited for Thai patients and suggested adjusting the medication’s dose in accordance with renal function.

Anti-Factor Xa Activity of Standard and Japan-Specific Doses of Rivaroxaban in Thai Patients With Non-Valvular Atrial Fibrillation

BACKGROUND

Recommended rivaroxaban doses for stroke prevention in atrial fibrillation (SPAF) are 20 and 15 mg/day in patients with normal and reduced renal function, respectively, but lower doses (15 and 10 mg) have been tested and approved in Japan. It is not known whether 15 and 10 mg rivaroxaban are appropriate in other Asian populations. This study compared the anti-Factor Xa (FXa) activity of 20 and 15 mg rivaroxaban in Thai patients with normal renal function and 15 and 10 mg rivaroxaban in patients with reduced renal function.Methods and Results:Sixty non-valvular atrial fibrillation patients receiving rivaroxaban (mean [±SD] age 69.3±9.1 years, mean creatinine clearance 59.2±22.7 mL/min) were enrolled. The anti-FXa activity of standard rivaroxaban and Japan-specific doses was measured at peak and trough concentrations. Median anti-FXa activity at peak concentrations was significantly higher for the standard than Japan-specific dose. Median anti-FXa activity measured at the trough was significantly higher for the standard dose only in those with impaired renal function. A higher proportion of patients receiving the Japan-specific rather than standard dose had anti-FXa activity at peak concentrations within the expected range (87.7% vs. 64.4%; P=0.001). One-third of those receiving the standard dose had anti-FXa activity higher than the expected range.

CONCLUSIONS

A significantly higher proportion of Thai patients receiving the Japan-specific dose of rivaroxaban had anti-FXa activity at peak concentrations within the expected range.