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The blood-thinning combination won't increase a patient's risk of early death, according to a new study presented Sunday at the annual meeting of the American Heart Association in Chicago. The report was also published online Nov. 16 in The Lancet.
Analysis of data from more than a dozen clinical trials revealed no increase in death rate if heart patients took both drugs together for long periods of time, said study co-author Dr. Laura Mauri, an associate professor of cardiovascular medicine at Harvard Medical School in Boston.
"Patients should not be afraid of taking these medications," Mauri said. "In fact, it's important they continue to take them as directed, because they can be life-saving."
The U.S. Food and Drug Administration issued a drug safety communication based on the results of the analysis that said that the benefits of the drugs "continue to outweigh their potential risks," which include excessive bleeding.
"Patients should not stop taking these drugs because doing so may result in an increased risk of heart attacks, blood clots, strokes and other major cardiovascular problems," the FDA statement said. "Health care professionals should not change the way they prescribe these drugs at this time."
Following a stroke or heart attack, patients often are prescribed medications that reduce blood clots by interfering with clotting cells called platelets. These antiplatelet drugs reduce the risk of a follow-up stroke or heart attack.
Aspirin is a mainstay blood thinner, and doctors often combine aspirin with newer anti-clotting drugs like clopidogrel (Plavix) or prasugrel (Effient), the researchers said in background material.
But a pair of recent clinical trials revealed an unexpectedly high death rate associated with the combination, raising concerns that using the drugs together could be harming patients in some unknown way, Mauri said.
For example, the Dual Antiplatelet Therapy (DAPT) trial -- another study presented at the AHA meeting in Chicago -- showed significant benefits for extending the combination therapy longer than the clinical standard of 12 months in heart attack patients who've received a stent to reopen a blocked artery.
The combination therapy reduced the risk of heart attack by about half if it was continued for up to 30 months compared with patients only taking aspirin, the trial found. The dual therapy patients also had a 71 percent reduced risk of dangerous blood clots forming inside their stents, according to the DAPT study.
Despite these positives, DAPT trial patients taking the two drugs also appeared to have a 36 percent increased risk of death during the study period compared with patients taking just aspirin.
"We thought it was important to see if there are any major risks we should be concerned about," said Mauri, who was lead investigator in the DAPT study.
To investigate their concerns, researchers reviewed data from 14 different clinical trials involving combination antiplatelet drug therapy. The trials included nearly 70,000 patients.
The analysis found no significant difference in rates of death between people who took the combination therapy for longer than 12 months, compared with people who received either aspirin alone or the dual therapy for shorter periods of time.
The increased death rates in the DAPT study appear to be mainly caused by people with prior diagnoses of cancer being randomly assigned to the patient group receiving combination therapy, Mauri said. When these patients were excluded, the differences in death rate were no longer significant.
"We were very reassured by the findings," Mauri said. "These important medications are not associated with an increased risk of death."
The results definitely provided comfort to Dr. Robert Harrington, chairman of AHA's 2014 Council on Scientific Sessions Programming and chair of the Stanford University department of medicine.
Harrington is an interventional cardiologist. Based on the safety analysis and the results of the DAPT trial, he plans to talk with his heart patients about the benefits of extending the dual drug therapy beyond the usual 12 months.
"If you are tolerating the drugs, I'm likely to continue it with you," Harrington said.
While her DAPT clinical trial prompted the analysis, Mauri said this proved a valuable safety review to perform on a combination therapy that has been widely used for at least a decade.
"It's good to take stock of something we take for granted, and know that we're doing things the right way," she said.
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SOURCES: Laura Mauri, M.D., associate professor, cardiovascular medicine, Harvard Medical School, Boston; Robert Harrington, M.D., chairman, AHA's 2014 Council on Scientific Sessions Programming, and chair of the department of medicine, Stanford University School of Medicine, Calif.; Nov. 16, 2014, The Lancet, online