Anti-stroke blood thinner shows promise in large clinical trials

In new and extensive clinical trials an experimental blood thinner called rivaroxaban is at least as good at preventing strokes as the drug warfarin – that has been the most widely used agent for the past five decades in people with erratic heartbeats called atrial fibrillations. Researchers said this Monday that this drug also sharply reduces the risk of major bleeding that is seen with warfarin.

An estimated 2.3 million Americans suffer from atrial fibrillation, in which the heart beats erratically and cannot pump blood effectively, causing blood clots to form. These clots may lead to a higher risk of stroke, heart attacks and death. An estimated 15% of strokes are caused by atrial fibrillation. Most people with atrial fibrillation could benefit from the new drugs, experts said, and analysts estimate the market for drugs in this class could top $20 billion a year.

Dr. Douglas Zipes of the Indiana University School of Medicine, a former president of the American College of Cardiology who was not involved in the research said both heart rate and the rhythm of heartbeats are important in predicting survival. He added, “It’s very easy to give a beta blocker to control rates… Now we have a once-a-day drug to control [problems caused by] rhythm, giving us very simple, straightforward treatment of atrial fibrillation.”

According to Dr. Shephal Doshi, director of electrophysiology and pacing at St. John's Health Center in Santa Monica, “For most patients, this will change the way we manage them and give them a better quality of life than [warfarin]. They will not have to constantly get their blood levels [of anti-coagulant] checked and will have much more freedom of diet…We’ve received more e-mails from patients about these two drugs [Pradaxa and rivaroxaban] than about any other therapeutic thing.” Pradaxa, known generically as dabigatran, is one such drug. It was approved two weeks ago by the Food and Drug Administration. It is taken twice daily.

Warfarin has been the mainstay of therapy till date and has been associated with life-threatening bleeding. Even in the best clinical trials, only about 70% of patients are able to keep the drug within the desired therapeutic range. Anything over the range could trigger bleeding tendencies. Thus there was “an intense search for alternatives” says Dr. Elaine Hylek of the Boston University School of Medicine.

Rivaroxaban, developed by Johnson & Johnson and Bayer HealthCare and brand-named Xarelto, is set to be approved by the FDA. Analysts predict that is likely to happen next year.

For the study Dr. Robert M. Califf of the Duke University School of Medicine and his colleagues studied 14,269 atrial fibrillation patients at 1,215 medical centers in 45 countries. Dr. Califf said at the Chicago meeting of the American Heart Association, “This was a very high-risk population, with multiple medical problems where a lot of bad stuff could happen… They’re the patients we most need to protect because they are most vulnerable.” Median age of the study population was 73 and a quarter of them were over 78. They were randomized to receive either rivaroxaban or warfarin. Prelimnary analyses show that those taking rivaroxaban had a 21% reduction in risk of stroke, slightly fewer heart attacks and a slightly lower death rate than individuals who received warfarin. There was 40% less bleeding into the brain, and less fatal bleeding with rivaroxaban making it safer.

According to Dr. Zipes, “For the clinician, this is certainly a very positive step forward… It certainly will facilitate our care of the patients. The big question unanswered, of course, is will it be better than Pradaxa? That awaits further studies.”

However Edward Gerstenfeld, an atrial-fibrillation expert at University of Pennsylvania School of Medicine, who was not involved in the study said omitting warfarin for the new drugs may not be necessary for all patients. He said, “Most everyone will want to switch over… People out there on [warfarin], if they’re doing fine, I wouldn’t advise them to change.” He also added that it took him some time to adopt a new drug waiting to see whether its early use leads to problems not detected in clinical trials. Cost is another factor he said. Warfarin is cheaper costing just pennies a day, compared with $6.75 a day for dabigatran. “In an era where cost is so important, patients in systems where monitoring is simple and effective will probably continue on warfarin,” said Sidney Smith, cardiologist at University of North Carolina at Chapel Hill.

Dr. Ananya Mandal

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Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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