The prothrombin time does not predict the risk of recurrent venous thromboembolism or major bleeding in rivaroxaban-treated patients

INTRODUCTION: For treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE), rivaroxaban is given in fixed doses without routine coagulation monitoring. PATIENTS AND METHODS: To determine whether monitoring would enhance its benefit-risk profile, we examined whether peak and trough prothrombin time (PT) values measured in 3797 rivaroxaban-treated patients included in the EINSTEIN DVT and PE studies correlated with subsequent recurrent VTE and major bleeding. In addition, we examined the stability of PT values over time and the impact of clinical variables on PT values. RESULTS: The mean peak PT values at months 3 and 6 or 12 were 21.9 ± 5 and 21.7 ± 6.0 s, respectively, while the mean trough PT values at months 2 and 6 were 15.1 ± 5.1 and 15.3 ± 2.9 s, respectively. Although peak and through PT values were higher in females, and with older age, frailty, active cancer, low body weight, impaired renal function and use of moderate to strong inhibitors of CYP3A4 and/or P-glycoprotein, and were lower in patients taking strong CYP 3A4 inducers, the differences were small and results were overlapping. Neither peak nor trough PT values correlated with recurrent VTE or major bleeding. CONCLUSIONS: PT monitoring is unlikely to improve the benefit-risk profile of rivaroxaban in patients with DVT or PE. The study was registered at www.clinicaltrials.gov as #NCT00440193 (EINSTEIN-DVT) and #NCT00439777 (EINSTEIN-PE).