Pradaxa (dabigatran) is an oral factor Xa inhibitor that prevents clotting and has been approved as an effective alternative to the anti-coagulant warfarin (Coumadin). The marketed advantage for Pradaxa is that blood tests are not required to monitor dosage and its effectiveness. The FDA only approved the drug for prevention of thromboembolic stroke in patients with atrial fibrillation. The RE-LY Study used for FDA approval showed that dabigatran was as effective as warfarin. However, within 12 weeks of its approval in October 2010, it was reported that dabigatran was responsible for more serious adverse events than 98.7% of all other medications.