Real-World Rivaroxaban and Apixaban Levels in Asian Patients With Atrial Fibrillation.

This study aims to measure the plasma levels of rivaroxaban and apixaban among Asian patients with atrial fibrillation and compare the results with expected drug levels from clinical studies. A total of 73 patients taking rivaroxaban and 105 patients taking apixaban were enrolled. Peak and trough levels were measured using ultra-high performance liquid chromatography with tandem mass spectrometry. The percentage of those with drug levels within the expected range reported in clinical studies was significantly higher in the apixaban group than in the rivaroxaban group, both for trough (84.8% vs. 64.4%; P = 0.002) and peak levels (76.9% vs. 33.8%; P < 0.001). After adjusting for age, sex, kidney function, appropriate dose, and adherence, patients taking rivaroxaban were still less likely to have peak and trough levels within the expected drug levels. Our real-world data suggests that Asian patients taking rivaroxaban are more likely to have out-of-expected drug levels than those taking apixaban.