Abstract 11913: Early Nonadherence With Dabigatran and Rivaroxaban in Patients With Atrial Fibrillation

Background: Dabigatran and rivaroxaban are novel oral anticoagulants (NOACs) approved recently for stroke prevention in atrial fibrillation (AF). Although NOACs are more convenient than warfarin, their lack of monitoring, and for dabigatran, dosing frequency may predispose patients to nonadherence. Limited information is available on the adherence rates and related clinical outcomes for dabigatran and rivaroxaban in clinical practice. Methods: We conducted a population-based cohort study using administrative data of patients aged 65 years and over with AF, linking hospital discharge abstract and prescription claims databases in Ontario, Canada from April 2012 to March 2014. Nonadherence was measured as proportion of patients discontinuing dabigatran or rivaroxaban, defined as a gap in dabigatran or rivaroxaban prescription for ≥14 days within the first 6 months of therapy, and time to discontinuation. A multivariate Cox proportional hazards model was used to examine the association between drug discontinuation at any time, and the composite outcome of hospitalization for stroke, or death. Results: The cohort consisted of 15,857 dabigatran users and 10,119 rivaroxaban users, with women comprising 52% of each medication group. Mean age was 80.7±6.7 years for dabigatran, and 77.0±7.1 years for rivaroxaban patients. At 6-months, 36.5% of patients discontinued dabigatran (110mg: 37.4%; 150mg: 34.1%), while 32.1% of patients discontinued rivaroxaban. Median time to discontinuation was 240 days (IQR: 78-523) for dabigatran and 140 days (IQR: 52-283) for rivaroxaban. Risk of the composite outcome (stroke or death) was significantly higher for those who discontinued dabigatran [HR 1.78 (95% CI 1.62-1.95);p<0.0001] or discontinued rivaroxaban [HR 3.07 (95% CI 2.54-3.72);p<0.0001] compared with those who did not discontinue the medication. Conclusions: Within 6 months of initiation, discontinuation rates are high in clinical practice, with 1 in 4 patients discontinuing dabigatran, and 1 in 3 patients discontinuing rivaroxaban. There is an association between nonadherence with either dabigatran or rivaroxaban and significantly worse clinical outcomes following medication discontinuation.