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Background: Warfarin reduces the risk for ischemic stroke in patients with atrial fibrillation (AF) but increases the risk for hemorrhage. Dabigatran is a fixed-dose, oral direct thrombin inhibitor with similar or reduced rates of ischemic stroke and intracranial hemorrhage in patients with AF compared with those of warfarin. Objective: To estimate the quality-adjusted survival, costs, and cost-effectiveness of dabigatran compared with adjusted-dose warfarin for preventing ischemic stroke in patients 65 years or older with nonvalvular AF. Design: Markov decision model. Data Sources: The RE-LY (Randomized Evaluation of Long-Term Anticoagulation Therapy) trial and other published studies of anticoagulation. The cost of dabigatran was estimated on the basis of pricing in the United Kingdom. Target Population: Patients aged 65 years or older with nonvalvular AF and risk factors for stroke (CHADS2 score ≥1 or equivalent) and no contraindications to anticoagulation. Time Horizon: Lifetime. Perspective: Societal. Intervention: Warfarin anticoagulation (target international normalized ratio, 2.0 to 3.0); dabigatran, 110 mg twice daily (low dose); and dabigatran, 150 mg twice daily (high dose). Outcome Measures: Quality-adjusted life-years (QALYs), costs (in 2008 U.S. dollars), and incremental cost-effectiveness ratios. Results of Base-Case Analysis: The quality-adjusted life expectancy was 10.28 QALYs with warfarin, 10.70 QALYs with low-dose dabigatran, and 10.84 QALYs with high-dose dabigatran. Total costs were $143 193 for warfarin, $164 576 for low-dose dabigatran, and $168 398 for high-dose dabigatran. The incremental costeffectiveness ratios compared with warfarin were $51 229 per QALY for low-dose dabigatran and $45 372 per QALY for highdose dabigatran. Results of Sensitivity Analysis: The model was sensitive to the cost of dabigatran but was relatively insensitive to other model inputs. The incremental cost-effectiveness ratio increased to $50 000 per QALY at a cost of $13.70 per day for high-dose dabigatran but remained less than $85 000 per QALY over the full range of model inputs evaluated. The cost-effectiveness of highdose dabigatran improved with increasing risk for stroke and intracranial hemorrhage. Limitation: Event rates were largely derived from a single randomized clinical trial and extrapolated to a 35-year time frame from clinical trials with approximately 2-year follow-up. Conclusion: In patients aged 65 years or older with nonvalvular AF at increased risk for stroke (CHADS2 score ≥1 or equivalent), dabigatran may be a cost-effective alternative to warfarin depending on pricing in the United States. Primary Funding Source: American Heart Association and Veterans Affairs Health Services Research & Development Service. [ABSTRACT FROM AUTHOR]