From the NEJM:
Dabigatran is a new oral direct thrombin inhibitor. In patients with atrial fibrillation (Afib), dabigatran 110 mg po bid was associated with rates of stroke and systemic embolism that were similar to those associated with warfarin, as well as lower rates of major hemorrhage.
Dabigatran 150 mg po bid, as compared with warfarin, was associated with lower rates of stroke and systemic embolism but similar rates of major hemorrhage
In previous studies of anticoagulation in Afib, the combination of clopidogrel and aspirin was more effective than aspirin alone but less effective than warfarin.
Subcutaneous idraparinux was more effective than warfarin but was associated with a substantially higher risk of bleeding. Ximelagatran, an earlier direct thrombin inhibitor, appeared to be similar to warfarin with respect to efficacy and safety but was found to be hepatotoxic. There was no evidence of hepatotoxicity with dabigatran.
The most devastating complication of warfarin therapy is intracranial hemorrhage, especially hemorrhagic stroke. As compared with aspirin, warfarin doubles the risk of intracranial hemorrhage.
The finding that the rate of this complication with both doses of dabigatran was less than one third the rate with warfarin, without a reduction in the efficacy against ischemic stroke, suggests an important advantage of dabigatran.
Warfarin broadly inhibits coagulation (inhibiting factors II, VII, IX, and X and proteins C and S). By selectively inhibiting only thrombin, dabigatran may be preserving other hemostatic mechanisms in the coagulation system and thus potentially mitigating the risk of bleeding (more information available at the source link).
Dabigatran versus Warfarin in Patients with Atrial Fibrillation. Stuart J. Connolly et al. NEJM, 2009.
Image source: Dabigatran etexilate, Wikipedia, public domain.