WEDNESDAY, Oct. 20 (HealthDay News) -- The drug Pradaxa has been approved by the U.S. Food and Drug Administration to help prevent stroke in people with a type of abnormal heart rhythm called atrial fibrillation.

The drug may prove a new option for patients who now use standard blood thinners such as warfarin to control the heart condition.

More than 2 million Americans have atrial fibrillation, which occurs when the heart's two upper chambers beat quickly and out of sync, the FDA said Wednesday in a news release.

Pradaxa (dabigatran) is an anti-clotting drug that inhibits an enzyme involved in blood clotting. Clinical studies of the drug found that when compared with warfarin, people with atrial fibrillation had fewer strokes on Pradaxa than those on warfarin, the FDA said.

One such trial was presented in February at the American Stroke Association annual meeting in San Antonio. It included more than 3,600 patients with atrial fibrillation and a previous stroke who were randomly chosen to receive warfarin, a low dose of Pradaxa (110 milligrams) twice a day or a higher dose (150 mg) of Pradaxa twice a day for about two years.

The rate of stroke or transient ischemic attack (TIA, often called "mini- stroke") in those taking warfarin was about 2.7 percent a year and 2.3 percent a year for those taking Pradaxa, not a significant difference.

However, the lower dose of Pradaxa caused less bleeding and was easier to manage than warfarin, a famously difficult drug to administer and monitor.

"In contrast to warfarin, dabigatran is given in a fixed dose twice daily independent of body weight, sex, food, whatever, and you don't need to monitor the coagulation system," study author Dr. Hans-Christoph Diener, chairman of neurology at University Hospital in Essen, Germany, said during a news conference held during the meeting.

"In patients who already had a transient ischemic attack or stroke and suffer from atrial fibrillation, dabigatran is as effective as warfarin," he added. "And it's much easier to handle."

Patients receiving Pradaxa had more heart attacks than those taking warfarin, but the absolute difference was small, the authors stated. Also, Pradaxa patients had higher rates of gastrointestinal bleeding.

The study was funded by Boehringer-Ingelheim GmbH, which makes the drug.

Those findings were echoed by a study published last year in the New England Journal of Medicine. In that trial, also funded by the drugmaker, Pradaxa proved equal to warfarin in preventing dangerous venous clots, but much easier for doctors and patients to manage.

"For patients and health-care providers, dabigatran is a far more convenient drug than warfarin because it has no known interactions with foods and minimal interactions with other drugs and therefore does not require routine blood-coagulation testing," wrote the international team of researchers led by Dr. Sam Schulman of McMaster University and the Henderson Research Center in Hamilton, Ontario, Canada.

And last November, two other promising reports on Pradaxa were presented at the American Heart Association meeting in Orlando. Those studies found the drug to be safe and effective in preventing blood clots when patients were treated for acute coronary syndrome, a cluster of symptoms that might indicate a heart attack. It was also found superior to warfarin in preventing strokes in patients with atrial fibrillation.

Pradaxa, which is produced in 75 milligram and 150 milligram strengths, is not without side effects or risk, however. According to the FDA, as with other anti-clotting drugs, a potential side effect is life-threatening bleeding. Other potential adverse reactions include stomach discomfort or pain, nausea, heartburn and bloating.

"It's premature to say that a drug like dabigatran will take the place of warfarin," Dr. Bernard Gersh, a professor of medicine at the Mayo Clinic College of Medicine in Rochester, Minn., said at the time of last November's conference. "There will be a lot of discussion about cost and convenience. It's a twice-daily dose and there are some questions about a possible higher rate of heart attack. I don't think this is truly resolved yet, but I think we can say that for the first time we have seen a drug that certainly has the potential to be an alternative to warfarin, and maybe even superior."

More information

Visit the American Heart Association for more on blood thinners.