A new drug beats standard treatment in preventing strokes, shows study.
"Apixaban resulted in an additional 21 percent relative reduction in stroke and systemic embolism" compared to warfarin, Christopher Granger, a professor at Duke University in Durham, North Carolina and co-leader of the study, reported in a statement.
"It also resulted in a 31 percent relative reduction in major bleeding, as well as an 11 percent relative reduction in overall mortality."
Warfarin, developed in the 1950s, is taken by millions of people worldwide who have had or are at risk of having strokes.
Strokes occur when a blood clot blocks circulation of blood in the brain, causing damage that can result in partial paralysis, impaired speech or vision, and death.
Some 15 million people worldwide suffer stroke each year, according to the World Health Organisation (WHO). Approximately a third die, and another third are permanently disabled.
Up to a quarter of all strokes arise from atrial fibrillation.
In phase III clinical trials -- the last step before commercialisation -- Granger and colleagues divided more than 18,000 patients in 39 countries into two groups.
One group took five milligrammes of apixaban twice a day for an average of 1.8 years, and the other warfarin, which is adjusted in dosage depending on the result of frequent blood tests.
The new drug has another advantage, said Lars Wallentin, a director of the Uppsala Clinical Research Centre in Sweden and a co-author of the study.
Unlike warfarin, apixaban does not require constant monitoring to insure that the dosage remains within a desired range.
Warfarin levels can be thrown off by a change in diet, or other medications. Too high a dosage can result in blood being too "thin," leading to internal or uncontrolled bleeding in case of injury. Too low, and the medicine can lose its capacity to prevent clots.
"Only about half of patients (at risk of stroke due to atrial fibrillation) who should be treated are being treated," Granger said. "The disparity exists because warfarin treatment has several limitations."
Five million people in the United States and six million in the European Union suffer from atrial fibrillation, according to the drugmakers.
Apixaban is manufactured by the American pharmaceutical companies Bristol-Myers Squibb and Pfizer, which also funded the study.