Abstract
In the AMPLIFY clinical trial, apixaban was non-inferior to warfarin plus subcutaneous
enoxaparin bridge therapy in the treatment of acute venous thromboembolism (VTE) and
was associated with significantly less bleeding. This study evaluated their comparative
effectiveness and safety in routine clinical practice. A matched-cohort design and
data from four U.S. private health care claims databases were employed. Study population
comprised patients who initiated outpatient treatment with apixaban versus warfarin
(plus parenteral anticoagulant bridge therapy) within 30 days of their initial VTE
episode; apixaban and warfarin patients were matched on age, characteristics of VTE
episode, study database and propensity score. Major bleeding, clinically relevant
non-major (CRNM) bleeding and recurrent VTE during the 180-day (maximum) follow-up
period were compared using shared frailty models. During mean follow-up of 143 days
among apixaban patients (n = 17,878) and 152 days among warfarin patients (n = 17,878), incidence proportions for apixaban versus warfarin, respectively, were
1.7% versus 2.3% for major bleeding, 7.0% versus 9.4% for CRNM bleeding and 2.3% versus
2.9% for recurrent VTE. In shared frailty models, risks of major bleeding (hazard
ratio [HR] = 0.75, 95% confidence interval [CI] = 0.64–0.87), CRNM bleeding (HR = 0.77,
95% CI = 0.71–0.83) and recurrent VTE (HR = 0.80, 95% CI = 0.70–0.91) were lower for
apixaban versus warfarin. In this large-scale evaluation of VTE patients receiving
outpatient treatment with apixaban or warfarin in U.S. clinical practice, risks of
major bleeding, CRNM bleeding and recurrent VTE were significantly lower among patients
who received apixaban.
Keywords
apixaban - warfarin - venous thromboembolism - bleeding
