Comparison of rivaroxaban mono-therapy and standard-therapy adjusted by CYP2C9 and VKORC1 genotypes in symptomatic pulmonary embolism

Rationale: Pulmonary embolism (PE) is a life-threatening manifestation of venous thromboembolism. Rivaroxaban is an oral anticoagulant, which directly inhibits Factor Xa. The objective of the current study was, in comparison to the standard-therapy method, to investigate the potential of rivaroxaban to improve the treatment of patients with PE, and to reduce hemorrhage in the standard-therapy group through adjusting the dose of warfarin by CYP2C9 and VKORC1 genotypes.

Methods: Sixty-two PE patients with or without deep venous thrombosis (DVT) was randomized to rivaroxaban mono-therapy or standard-therapy with enoxaparin followed by vitamin K antagonist (VKA). Concentration of the anticoagulants was adjusted according to the results of CYP2C9 and VKORC1 genotypes in order to stabilize the international normalized rate (INR) at 2.0-3.0 range. Length of hospital stay at initial hospitalization was compared, therapeutic efficacy was examined by computed tomographic pulmonary angiography (CTPA) and ventilation/perfusion (V/Q) scan, and side-effect of anti-coagulants was monitored at 1-month, and 3- or 6-months follow-up check points.

Results: We found that, overall, patients who received rivaroxaban mono-therapy had a significantly shorter length of hospital stay compared with patients who received standard-therapy of enoxaparin followed by VKA (9.29±3.70 versus 11.38±3.12days, P=0.021). The therapeutic efficacy was of no marked difference between these two groups. However, after one month treatment, 50% (16/32) of the standard-therapy group had mild hemorrhage, which was significantly higher than that of rivaroxaban mono-therapy group (16.7%, 5/30, P=0.006). Moreover, a significantly higher rate in the standard-therapy group (22.2% versus 3.4%, P=0.032) was found after 3 or 6months therapy. Major bleeding was slightly but not significantly higher in the standard-therapy group than that in the rivaroxaban therapy group. In addition, 2 (6.3%) patients died from Life-threatening bleeding in the standard-therapy group.

Conclusion: Findings of the current study suggested that rivaroxaban mono-therapy result in shorter hospital stay compared to the standard-therapy. Implication of CYP2C9 and VKORC1 genotypes in determining dose of warfarin, however, remains to be further examined in larger cohort studies.