When used by patients with
mechanical heart valves, the blood thinner Pradaxa raises the risk of both
dangerous clots and bleeding around the heart, a new study says.
The bottom line for lead
researcher Dr Frans Van de Werf, chairman of the department of cardiovascular
medicine at the University Hospitals Leuven in Belgium, is "don't use
Pradaxa in patients with a mechanical valve."
In fact, the trial was
halted early and the US Food and Drug Administration subsequently issued a "black box" warning that said this particular group of heart patients should
not take Pradaxa because of an increased chance of a stroke or heart attack.
Pradaxa (dabigatran) is a
drug that prevents clotting. It has been approved as an alternative to warfarin
for patients with an abnormal heartbeat called atrial fibrillation, the
"It was hoped that a
novel oral direct clotting inhibitor would provide similar or better protection
for patients with mechanical heart valves without the need for [the] monitoring
or dietary restrictions associated with warfarin," said Dr Gregg Fonarow,
a professor of cardiology at the University of California, Los Angeles.
Risk for severe bleeding
After a heart valve
replacement, patients are typically put on blood thinners or drugs that combat
clotting to prevent a heart attack or stroke, but the danger of these drugs is
a risk for severe bleeding.
"While the vitamin K
antagonist warfarin is very effective at preventing clotting-related
complications of mechanical heart valves, its use requires lifetime monitoring,
with at least monthly blood tests, dietary restrictions and the potential for
multiple medication interactions," Fonarow explained.
randomised clinical trial showed that Pradaxa was even more problematic than
warfarin in terms of side effects, he said.
"As a result of these
findings, the FDA added a 'black box' warning to the medication label warning
against using dabigatran and similar medications in patients with mechanical
heart valves," Fonarow said.
The report was published in the New England Journal of Medicine and the trial was funded
by Boehringer Ingelheim, the maker of Pradaxa.
Pradaxa or warfarin
For the study, an
international team of researchers randomly assigned 252 patients who had an
aortic or mitral valve replacement to either Pradaxa or warfarin. Some patients
had the valve replacement within a week before the study began and others had
the surgery three months earlier, the researchers noted.
Of those taking Pradaxa, 32%
had their treatment stopped or dose changed. In addition, 5% of those on the drug suffered a stroke,
compared with none of those taking warfarin.
Moreover, 4% of those
taking Pradaxa had major bleeding around the heart, compared with 2% of those
taking warfarin, the researchers found.
For more on heart valve
replacement, visit the American Heart Association.