A Step In The Wrong Direction: The Lack Of Drug Subsidies Drives Patients To Switch From Direct Oral Anticoagulants To Warfarin

Background: Direct oral anticoagulants (DOACs) are superior to warfarin in preventing ischemic stroke from nonvalvular atrial fibrillation (AF). Transitioning from a DOAC to warfarin is rarely medically indicated. The frequency and determinants of switching from DOAC to warfarin, including the potential influence of cost, are not known. Objective: Examine the impact of financial assistance available through Medicaid prescription coverage or low-income subsidy programs on likelihood of switching to warfarin after initiating a DOAC. Methods: We identified patients in the Medicare 5% sample who initiated a DOAC from 2015 to 2017. Patients were eligible if they were age 65 or older, had AF diagnosis, had no oral anticoagulant use during the prior 12 months, and were enrolled in a Medicare Prescription Plan for at least 12 months prior to first oral anticoagulant. Patients who switched to warfarin after an initial DOAC were identified, and their characteristics were evaluated in bivariable and multivariable analyses using Cox regression to adjust for potential confounders and censor for death or end of the observation period. Results: Of 27,151 eligible patients,16,599 (61%), 8,930 (33%), and 1,622 (6%) initiated apixaban, rivaroxaban, and dabigatran, respectively. 30% (8,110) initiated a low dose DOAC. A total of 1,481 (5.5%) switched to warfarin sometime during the follow-up period. The median time to first warfarin dose among patients who switched was 153 days. Overall, 14% of patients were eligible for Medicaid prescription coverage and an additional 8.8% were eligible for other drug subsidies; these patients were significantly less likely to switch to warfarin, compared to other patients (3.4%, 4.1%, 5.8% of patients with Medicaid coverage, other drug subsidies, or neither). After risk adjustment, the relative hazard of switching to warfarin was 0.57 (95% confidence interval (CI): 0.47-0.68) and 0.69 (95% CI: 0.56-0.85), for patients with Medicaid coverage or drug subsidy, respectively, compared to other patients. Conclusions: The financial burden of DOACs may contribute to patients switching to warfarin, despite guideline recommendations. Financial assistance may facilitate evidenced-based best practices in stroke prevention.