MONDAY, July 16 (HealthDay News) -- A new study helps douse fears about possible harmful interactions when heart patients take both the anti-clotting drug clopidogrel and a cholesterol-lowering statin.

Those fears arose several years ago when researchers showed that the same enzyme metabolizes both clopidogrel and the various statins, explained Dr. Steven R. Steinhubl, an associate professor of medicine at the University of Kentucky, and a member of the team reporting the finding in the July 24 issue of the Journal of the American College of Cardiology.

"The original study made a lot of sense," Steinhubl said. "The mechanism of action was demonstrated very well. Since then, there have been a dozen other studies. About a third showed the same interaction, a third showed nothing, and a third showed the opposite -- a beneficial interaction."

Because of the results of the new study, "I tend to support the idea that this is not a clinically important interaction," Steinhubl said.

The new study used data from a trial called CHARISMA, which created a sensation last year when it showed that adding clopidogrel (Plavix) to aspirin for patients who had suffered a heart attack or stroke did not improve their survival. In this study, the researchers looked at just over 10,000 patients who got a statin as well as clopidogrel to see whether the combination therapy increased the incidence of heart attack, stroke or cardiovascular death over 28 months.

It didn't. The rate of such deadly interactions was 6.8 percent for those getting clopidogrel and a statin, and 7.3 percent for those getting a statin but not clopidogrel.

"It is potentially a big deal, because lots of patients who need to be on clopidogrel also need to be on a statin," said Dr. Deepak L. Bhatt, associate director of the Cleveland Clinic cardiovascular coordinating center and another member of the research team. "But if there is some kind of interaction, we didn't see it, although we didn't necessarily disprove it. It is below the level of natural drug variability."

Fears of the possible interaction have been fading, both Bhatt and Steinhubl said. "I don't know of any situation where people are changing their practice because of it," Steinhubl said.

"The bottom-line message to patients is that there was some concern about a possible interaction a couple of years ago," Bhatt said. "But, in a practical sense, there is nothing that patients now need to worry about."

Other findings unrelated to statins have emerged as researchers pore over data from the CHARISMA trial, which enrolled more than 15,000 patients, Bhatt said. One such finding, published last month, is that the aspirin-clopidogrel combination appears to have some benefit for people in the highest risk group -- those who have had a heart attack or stroke, or a history of rupture of an artery-blocking fatty deposit called a plaque, he said.

But the postulated dangers of the clopidogrel-statin combination appear not to have stood up to close examination, Bhatt said.

More information

Learn more about clopidogrel from the U.S. National Library of Medicine.