Although warfarin has been, for more than 20 years, the gold standard for reducing stroke in atrial fibrillation, it has many problems. Warfarin therapy needs to be monitored by blood test measurements. Many patients cannot take this drug and there is a significant risk of increased bleeding.
In a major international trial, researchers from McMaster University are reporting the results of research on a new blood thinner, dabigatran (Pradax or Pradaxa). In this study, dabigatran has been shown to be superior to warfarin for the reduction of stroke and also for reducing bleeding complications, especially bleeding into the brain. The study is to be presented today at the European Society of Cardiology Congress in Barcelona, Spain.
Atrial fibrillation is a common disorder of the heart rhythm that affects about one percent of the population and up to 10% of people over the age of 80. The major complication of atrial fibrillation is stroke. About one in six strokes are due to atrial fibrillation. Patients who have atrial fibrillation have an annual risk of stroke between one to 10%. Blood thinners such as warfarin are the only way to prevent these strokes.
Several new drugs have been recently studied to see if they could replace warfarin. None, however, has been satisfactory either because they were not effective enough; they had too many side effects or they caused too much bleeding.
The results of the RE-LY study, which compared dabigatran to warfarin in patients with atrial fibrillation at risk for stroke, clearly show that dabigatran is superior to warfarin. This is the first time in more than 50 years that a new oral blood thinner has been developed which has been found to be both safer and more effective than existing therapy.
"Although researchers have been looking for a replacement for warfarin for several decades, nothing has been successful," said Dr. Stuart Connolly, a professor of medicine, director of the Division of Cardiology of the Michael G. DeGroote School of Medicine at McMaster University and one of the leading investigators of the RE-LY study (Randomized Evaluation of Long-term anticoagulant therapY).
The RE-LY study compared two doses of dabigatran with the current standard therapy, warfarin, in 18,113 patients with atrial fibrillation at increased risk of stroke. The study included more than 965 centres in 44 countries. Patients were enrolled over a two-year period and then followed for one further year. The study closed follow-up in March, 2009.
"The importance of the results for the RE-LY study are hard to overestimate," said Dr. Salim Yusuf, director of the Population Health Research Institute at McMaster University and Hamilton Health Sciences in Hamilton. "The results are much better than we had hoped for. It is especially good that we have two doses of dabigatran that are effective and superior to warfarin in different ways."
Dr. Connolly predicts that dabigatran will "change the way we treat patients who have atrial fibrillation at risk of stroke. It will increase the number of patients who are able to take blood thinners safely and this will in turn greatly reduce the number of patients with atrial fibrillation suffering a stroke or dying."
The RE-LY study was designed to evaluate whether either of two doses of dabigatran was non-inferior to warfarin. In other words, it was designed to see if either of the two doses of dabigatran was at least as good as warfarin. The results show, however, that the higher dose, 150 mg twice daily, significantly reduces the risk of stroke by 34% compared to warfarin, with similar rates of major bleeding. The lower dose of dabigatran, 110 mg twice daily, was similar to warfarin in respect to stroke, with significantly less major bleeding.
The study was overseen by researchers from McMaster University; the Uppsala University in Sweden and the Lankenau Institute for Medical Research in the U.S. The study was co-ordinated by the Population Health Research Institute and sponsored by Boehringer-Ingelheim.
For further information: and to arrange interviews, please contact: Susan Emigh, Public Relations, Faculty of Health Sciences, McMaster University, Phone: (905) 525-9140, ext. 22555, Cell/Mobile: (905) 518-3642, E-mail:
emighs@mcmaster.ca
