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Updated: Aug 25, 2025
The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation
Published on: February 28, 2012
Formulary restrictions and stroke risk in patients with atrial fibrillation
Bo Zhou, Seth Seabury, Dana Goldman
1USC Schaeffer Center for Health Policy and Economics, 635 Downey Way, VPD 412D, Los Angeles, CA 90089-3333.
Insights
Formulary restrictions on non-vitamin K antagonist oral anticoagulants (NOACs) reduced their use and adherence in atrial fibrillation patients. This led to a higher risk of mortality and stroke, highlighting the need for policy review.
Area of Science:
- Cardiovascular Medicine
- Pharmacoeconomics
- Health Outcomes Research
Background:
- Non-vitamin K antagonist oral anticoagulants (NOACs) are crucial for preventing stroke in atrial fibrillation (AF).
- Formulary restrictions, such as prior authorization and step therapy, may impact NOAC utilization and patient outcomes.
- Understanding the effects of these restrictions is vital for optimizing anticoagulation therapy.
Purpose of the Study:
- To evaluate the impact of formulary restrictions on NOAC use among Medicare beneficiaries with newly diagnosed AF.
- To assess the association between these restrictions and key health outcomes, including mortality and thromboembolic events.
Main Methods:
- A longitudinal cohort study of Medicare beneficiaries diagnosed with AF between 2011 and 2015.
- Comparison of anticoagulant use and health outcomes based on Medicare Part D plan coverage of NOACs.
- Utilized Cox proportional hazards models to analyze the association between formulary restrictions and adverse events.
Main Results:
- Beneficiaries in plans with restricted NOAC access showed lower NOAC use, worse adherence, and longer prescription delays.
- Restricted plans were associated with a significantly higher aggregate risk of mortality, stroke, and transient ischemic attack (adjusted HR, 1.098).
Conclusions:
- Formulary restrictions on NOACs may worsen existing underuse and increase stroke risk in newly diagnosed AF patients.
- Pharmacy benefit managers and Part D plans should re-evaluate formulary policies to ensure patient access to effective anticoagulants.
Objectives:
To determine the use of formulary restrictions (prior authorization and step therapy) on the use of non-vitamin K antagonist oral anticoagulants (NOACs) and their effect on health outcomes.
Study Design:
Longitudinal cohort study. We identified a sample of Medicare beneficiaries with an incident diagnosis of atrial fibrillation (AF) in 2011 to 2015 and followed them until the end of 2016 or death. We compared anticoagulant use and health outcomes associated with Medicare Part D plan coverage of NOACs.
Methods:
The primary outcomes were composite rates of death, stroke, transient ischemic attack, and systemic embolism. We used Cox proportional hazards models to estimate the association between formulary restrictions and adverse health outcomes.
Results:
Beneficiaries enrolled in Part D plans that restricted access to NOACs had a lower probability of NOAC use (30.2% vs 32.2%), worse adherence conditional on NOAC use (32.1% vs 34.3% adherent), and longer delays in filling an initial prescription (46% vs 55% filled within 30 days of AF diagnosis). Beneficiaries in restricted plans had higher aggregate risk of mortality/stroke/transient ischemic attack (adjusted HR, 1.098; 95% CI, 1.079-1.118).
Conclusions:
Limiting access to NOACs may exacerbate current underuse of anticoagulants and increase the risk of stroke among patients with newly diagnosed AF. Pharmacy benefit managers and Part D plans need to continuously review the appropriateness of formulary policies to ensure patient access to effective medications.
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