Aug. 10, 2011 -- The newly approved drug Xarelto appears to prevent strokes at least as well as the standard treatment warfarin in people who have a heart condition that puts them at high risk for blood clots, a study shows.
Xarelto was approved by the FDA in July to prevent dangerous blood clots in people having hip and knee replacement surgery.
Next month, a panel of experts will consider whether the agency should also approve its use as a once-daily treatment for atrial fibrillation.
"Warfarin, which we found in the '50s and '60s, is a very good drug in preventing stroke, but it's sometimes difficult to use," says study researcher Manesh R. Patel, MD, a cardiologist at Duke University.
Because it works by blocking vitamin K, foods that are high in that nutrient, like dark leafy greens, can make warfarin less effective. A host of other medications including some antibiotics and painkillers can interact with the drug, blocking or enhancing its effect.
Doctors typically require patients on warfarin to get monthly blood tests to make sure it's working properly and "not making the blood too thick or too thin, so to speak," Patel says.
Comparing Xarelto to Warfarin
A new study, published in The New England Journal of Medicine, tested Xarelto against warfarin in more than 14,000 patients with atrial fibrillation.
The patients in the study were deemed to be at moderate to high risk of stroke, either because they'd had a stroke before or because they had heart failure, high blood pressure, diabetes, or they were older than age 75.
Patients were randomly assigned to take either a daily dose of warfarin or Xarelto. To prevent people from knowing which treatment they were getting, both groups were also assigned to take a placebo pill.
Most patients were followed for about two years.
During that time, 269 people taking Xarelto and 306 people taking warfarin suffered strokes or had a blood clot that lodged somewhere else in the body, proving the drugs to be roughly similar.
"I think it's a reasonable alternative to warfarin. It's at least as good as warfarin," says Patel.
It doesn't require frequent trips back to the doctor, he tells WebMD, "so from a patient's perspective, it represents a potential alternative to the current standard."
Significant bleeding, an expected risk of drugs that keep blood from clotting, occurred in 1,475 patients taking Xarelto and 1,449 patients taking warfarin.
But people on Xarelto were less likely to experience bleeding in their brains or fatal bleeding than those on warfarin.
Experts say Xarelto may be less likely to cause bleeding in the brain than warfarin because it's a more targeted drug.
In the body, a chain of chemical reactions leads to blood clotting. Warfarin interferes with four steps in that chain, while Xarelto only blocks one part of the reaction, an enzyme called factor Xa.
Weighing Benefits and Risks
Gregory J. del Zoppo,MD, a hematologist and professor of medicine at the University of Washington School of Medicine, says the main benefit of this drug and several similar agents, including the drug Pradaxa, which was approved by the FDA last year to treat atrial fibrillation, is likely to be convenience.
"To have something that's easier to manage and takes less involvement is probably useful," he says, particularly for older patients who may have trouble keeping up with their medication.
But he says there are several potential downsides of the newer drugs that patients need to understand.
One is cost. The newer drugs cost between $6 and $9 a day to take compared to warfarin, which is available generically for $4 a month through several large U.S. retailers.
And he says while doctors know how to quickly reverse the effects of warfarin in the case of dangerous bleeding, it's less clear how to manage uncontrolled bleeding with the newer agents.
"The one worry I have with these agents is that so far we don't have a way of reversing their effect if we need to," del Zoppo says. "What happens when something goes wrong? And indeed, I think the companies are thinking about this."