LAUSR

BACKGROUND The factor Xa inhibitors have been widely used for the treatment and prevention of venous thromboembolism (VTE). However, the efficacy of factor Xa inhibitors in Japanese patients with VTE has not been well examined. In this study, we investigated the effect of the sequential use of two factor Xa inhibitors in patients with acute VTE. METHODS We conducted an observational study of 87 consecutive patients diagnosed with VTE. As an initial treatment, we administered subcutaneous fondaparinux to the patients for 7-10 days, and then switched to oral rivaroxaban. The symptoms and findings were assessed after the initial treatment and after using rivaroxaban for 7-14 days. We evaluated the deep vein thrombosis (DVT) in the legs using our own scoring system [quantitative ultrasound thrombosis (QUT) score]. RESULTS Of the 87 patients, 33% had symptoms, half had pulmonary embolism (PE), and 95% had DVT of the legs. Out of the 87 patients, VTE worsened during the administration of fondaparinux in 4 patients. All of them had experienced malignancy, and died within 6 months. Of two patients developing bleeding, one patient required a transfusion. Eventually, this strategy was effective in 80 patients and had no change in one. The D-dimer level was significantly reduced by fondaparinux (17.8μg/ml±16.0μg/ml vs. 8.3μg/ml±7.2μg/ml, p<0.0001), followed by rivaroxaban (8.3μg/ml±7.2μg/ml vs. 5.5μg/ml±4.9μg/ml, p<0.0001). Similarly, the QUT score was improved by fondaparinux (4.7±2.6 vs. 2.5±2.5, p<0.0001), and further reduced by rivaroxaban (2.5±2.5 vs. 1.9±1.8, p<0.0001). CONCLUSIONS A treatment strategy using subcutaneous fondaparinux followed by oral rivaroxaban is effective for treating acute VTE in Japanese patients.