What's the best blood thinner if you have a-fib?
(HealthDay)—People with the heart condition atrial fibrillation often use blood thinners to help prevent a stroke. Now a new study suggests one of those medications might stand out as safer and more effective.
Researchers found that a-fib patients on the drug Eliquis (apixaban) had a slightly lower risk of blood clots and stroke than those on Xarelto (rivaroxaban)—a clot-preventing drug in the same class. They were also significantly less likely to suffer gastrointestinal bleeding as a side effect of their medication.
However, experts stressed that the findings do not prove that Eliquis is better—in large part because they are based on patients' health insurance records.
"The highest-quality evidence comes from controlled clinical trials," explained lead researcher Dr. Michael Fralick, of the University of Toronto and Mount Sinai Hospital in Toronto.
He was referring to studies where researchers randomly assign patients to take a certain treatment, then track their outcomes.
Research comparing Eliquis and Xarelto head-to-head is underway, Fralick noted—and the results should give a clearer answer in the near future.
Other cardiologists not involved in the study said it had too many limitations to draw conclusions.
"This is not going to affect clinical practice," said Dr. Dhanunjaya Lakkireddy, chair of the electrophysiology section and leadership council for the American College of Cardiology.
He said the message to Xarelto patients is, "The sky is not falling."
Atrial fibrillation affects 3 to 6 million Americans, according to the U.S. Centers for Disease Control and Prevention. It arises when the heart's upper chambers (the atria) beat erratically instead of maintaining a normal rhythm.
The problem is not immediately life-threatening, but it can allow blood to pool in the atria. When that happens, a blood clot can form, and potentially be pumped from the heart and into a blood vessel supplying the brain—causing a stroke.
That's why people with a-fib commonly take clot-preventing drugs (anticoagulants) like Eliquis and Xarelto.
They belong to a newer class of medications called direct oral anticoagulants, or DOACs. Guidelines recommend that most a-fib patients take a DOAC rather than an older medication, warfarin, because they are safer, more effective and easier to take.
But the guidelines say nothing about whether any one DOAC is better than another.
"That's why we wanted to do this study," Fralick said.
The researchers analyzed health insurance claims from nearly 79,000 U.S. adults who started on Eliquis or Xarelto between 2012 and 2019. Each Eliquis patient was "matched" to a Xarelto patient who was similar—in age, coexisting health conditions, prescriptions and other factors.
On average, the study found Eliquis patients did better. Their risk of a stroke or other blood clot was 18% lower—at a rate of 6.6 per 1,000 patients per year, versus 8 per 1,000 among Xarelto patients.
When it came to safety, the advantage was bigger. Eliquis patients had a 42% lower risk of internal bleeding: They suffered bleeding problems at a rate of about 13 per 1,000 each year, compared with 22 per 1,000 in the Xarelto group.
The difference was mainly seen in stomach bleeding, the researchers said.
The study, published March 10 in the Annals of the Internal Medicine, was funded by Brigham and Women's Hospital in Boston. Fralick was based there at the time of the study.
Lakkireddy cautioned that the results are based on "incomplete data" from insurance records that leave many questions open. For example, he said, Eliquis patients were a bit older, so their medication doses might have been lower—which would reduce the chances of bleeding.
Lakkireddy—who gets speaking fees from both of the drugmakers, Pfizer and Janssen—also pointed to the bigger picture: Since the medications' debut, there has been "hair-splitting" over which is better, along with marketing battles.
But what's clear, he said, is that the newer drugs are better than warfarin.
Dr. Gregg Fonarow, another cardiologist not involved in the study, had similar caveats.
There could be other differences between the two patient groups that help explain the findings, said Fonarow, a professor of cardiovascular medicine and science at the University of California, Los Angeles.
If both drugs are from the same family, why would one be any better than other?
"Even when drugs are from the same class, there is variability among them," Fralick explained. "There's lab research that suggests the blood-thinning with [Eliquis] is more stable and consistent."
That suggests it's less likely to either trigger bleeding or fail to prevent clots, Fralick said. However, whether lab research translates into real life is unclear.
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