WEDNESDAY, Sept. 1 (HealthDay News) -- More isn't necessarily better when prescribing the two drugs commonly used to treat patients who are in danger of having a heart attack, Plavix (clopidogrel) and aspirin, a new study suggests.
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Two reports on the data find that high doses of Plavix are good for some patients, but not all, while high-dose aspirin is no better than a low dose for preventing new heart attacks, other cardiac problems, stroke and death.
The findings suggest a need to assess the risks and benefits individually, experts say.
Patients who are at high risk for heart attack and stroke and low risk for bleeding are going to do well on a higher dose of Plavix, said Dr. Gregg Stone, author of an editorial in The Lancet.
"Patients who are at lower risk for atherosclerotic complications, but high risk for bleeding should be treated with a more conservative lower dose," added Stone, director of cardiovascular research and education at Columbia University Medical Center in New York City.
The reports are being released Wednesday to coincide with the meeting of the European Society of Cardiology in Stockholm. They are also published in the Sept. 1 online edition of The Lancet and in the Sept. 2 issue of the New England Journal of Medicine.
While aspirin and Plavix are mainstays of treatment for those at risk of having a heart attack, questions remain about proper dosing. Too little medicine won't prevent clotting, which can lead to heart attack, while too much can cause fatal bleeding.
To assess the best treatment regimens, the researchers assigned 25,086 patients at risk of having a heart attack (due to acute coronary syndrome) to a standard dose or double dose of Plavix and to high- or low-dose aspirin. Patients on the standard dose of Plavix got 300 milligrams (mg) the first day followed by 75 mg daily, while those with the double dose took 600 mg on day one, followed by 150 mg for six days and 75 mg thereafter. Patient outcome was evaluated after 30 days.
About two-thirds of the patients underwent percutaneous coronary intervention (PCI), also known as angioplasty. This involved threading a catheter with a balloon at the end through a blocked or narrowed coronary artery and placing a small mesh tube, called a stent, in the artery to keep it open.
After angioplasty, patients typically receive both Plavix and aspirin to reduce the likelihood of clotting and re-blocking the artery or the stent.
The researchers found that patients undergoing angioplasty benefited from a double dose of Plavix, with their risk of heart attack, stroke or death reduced 14%, compared with patients who were given a standard dose. Moreover, the risk of clotting in the stent was cut 46% among those receiving the double dose.
However, the double-dose patients had a 41% increased risk of bleeding compared to those getting the standard dose. This led the researchers to recommend a standard dose for patients not having angioplasty.
As for aspirin, no difference in adverse events was seen among patients taking a high (300 or 325 mg) or low (75 to 100 mg) dose. The researchers concluded that low-dose aspirin is best, since it reduces the risk of bleeding without increasing the risk of clotting.
"Taken together, the message is very simple: We recommend that patients undergoing PCI receive the full double-dose regimen of clopidogrel, and those who do not have PCI should be treated with the standard-dose regimen of clopidogrel," said Dr. Shamir Mehta, an associate professor of cardiology at McMaster University in Ontario, Canada, and co-author of both reports.
Commenting on the study, another expert, Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, said he was surprised to find that the double dose wasn't beneficial overall and that it increased the risk of bleeding.
"A double dose of clopidogrel is an attractive option for patients with acute coronary syndrome undergoing coronary interventions compared with standard dosing," Fonarow said. "However, alternative antiplatelet agents, such as prasugrel (Effient) or ticagrelor (Brilinta), also have been proven to offer incremental benefits to standard dosing with clopidogrel."
The trial was funded by the pharmaceutical giants Sanofi-Aventis and Bristol-Myers Squibb, which make Plavix.
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SOURCES: Shamir Mehta, M.D., associate professor of cardiology, McMaster University, Hamilton, Ontario, Canada; Gregg Stone, M.D., director, cardiovascular research and education, Columbia University Medical Center, New York City; Gregg C. Fonarow, M.D., professor, cardiology, University of California, Los Angeles; Sept. 2, 2010, New England Journal of Medicine; Sept. 1, 2010, The Lancet, online