Abstract
BACKGROUND: Routinely used cardiac medications, based on pharmacokinetics, are hypothesized to increase drug levels of direct oral anticoagulants (DOACs), with the potential to increase the risk of hemorrhage. We set out to compare the risk for hemorrhage following initiation of amiodarone, verapamil, or diltiazem (moderate cytochrome P450 3A4 and/or P-glycoprotein activity) vs metoprolol or amlodipine (weak or no activity), among older adults prescribed DOACs. METHODS: We conducted a population-based, retrospective cohort study of all adults (aged ≥ 66 years) on a DOAC (dabigatran, apixaban, rivaroxaban; n = 295,038) who were newly prescribed amiodarone (n = 4872), verapamil (n = 1284), or diltiazem (n = 14,638), compared with metoprolol or amlodipine, from Ontario, Canada (2009-2016). The outcome was hospital admission or emergency room visit with a major hemorrhage (upper or lower gastrointestinal tract, intracranial), examined using weighted models. RESULTS: A total of 1737 hemorrhage events occurred (amiodarone, 80 [1.6%] vs metoprolol 503 [2.3%]; verapamil, 32 [2.5%] vs amlodipine, 406 [1.6%]; diltiazem, 312 [2.1%] vs amlodipine, 404 [1.5%]). The weighted risk of major hemorrhage was not elevated with amiodarone, verapamil, or diltiazem initiation in DOAC users, compared to metoprolol or amlodipine, during the full follow-up period (hazard ratio [HR; 95% confidence interval]: amiodarone HR 0.77 [0.61-0.97]; verapamil HR 1.32 [0.88-1.98]; diltiazem HR 0.99 [0.85-1.15]). This finding was consistent with a broader definition of bleeding, adjusting for kidney function, by DOAC type or dosage. CONCLUSIONS: Hemorrhage risk with amiodarone, verapamil, and diltiazem was similar to that with comparators, among DOAC users aged > 66 years.