According to research published early online in the New England Journal of Medicine, in patients with atrial fibrillation, the direct thrombin inhibitor dabigatran (at a high enough dose) prevents strokes and systemic emboli more effectively than warfarin.

The Randomised Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial was a randomised trial designed to compare two fixed doses of dabigatran, each administered in a blinded manner, with open-label use of warfarin in patients who had atrial fibrillation and were at increased risk for stroke.

The non-inferiority trial involved 18,113 patients with atrial fibrillation and a risk of stroke who were randomised to receive in a blinded fashion, fixed doses of dabigatran 110 mg or 150 mg twice daily or, in an unblinded fashion, adjusted-dose warfarin. The median duration of the follow-up period was 2.0 years. The primary outcome was stroke or systemic embolism.

 
The following results were reported:
• Rates of the primary outcome were 1.69% per year in the warfarin group, as compared with 1.53% per year in the group that received 110 mg of dabigatran (relative risk with dabigatran, 0.91; 95% confidence interval], 0.74 to 1.11; P<0.001 for non-inferiority) and 1.11% per year in the group that received 150 mg of dabigatran (relative risk, 0.66; 0.53 to 0.82; P<0.001 for superiority).
• The rate of major bleeding was 3.36% per year in the warfarin group, as compared with 2.71% per year in the group receiving 110 mg of dabigatran (P=0.003) and 3.11% per year in the group receiving 150 mg of dabigatran (P=0.31).
• The rate of hemorrhagic stroke was 0.38% per year in the warfarin group, as compared with 0.12% per year with 110 mg of dabigatran (P<0.001) and 0.10% per year with 150 mg of dabigatran (P<0.001).
• The mortality rate was 4.13% per year in the warfarin group, as compared with 3.75% per year with 110 mg of dabigatran (P=0.13) and 3.64% per year with 150 mg of dabigatran (P=0.051).

The authors concluded that in patients with atrial fibrillation, dabigatran given at a dose of 110 mg was associated with rates of stroke and systemic embolism that were similar to those associated with warfarin, as well as lower rates of major haemorrhage. Additionally, dabigatran administered at a dose of 150 mg, as compared with warfarin, was associated with lower rates of stroke and systemic embolism but similar rates of major haemorrhage.