WEDNESDAY, Oct. 6 (HealthDay News) -- Heartburn drugs known as proton-pump inhibitors can safely be taken with the blood thinner Plavix, a new study indicates.

There has been concern that these medications, called PPIs, might interfere with the ability of Plavix (clopidogrel) to do its job.

"This is reassuring data that there is not any clinically significant interaction between clopidogrel and PPIs," said lead researcher Dr. Deepak L. Bhatt, chief of cardiology at the Veterans Affairs Boston Healthcare System.

"This is contrary to prior observational, non-randomized studies that showed that if you took clopidogrel and a PPI, it blunted the ability of clopidogrel to protect from things like heart attack," he noted.

In addition, this is the first randomized clinical trial to show that prophylactic use of PPIs for patients taking Plavix reduces gastrointestinal bleeding, he said.

Doctors often prescribe the two drugs in combination to prevent clotting and reduce the risk of stomach bleeding, which can be a serious complication for patients taking Plavix.

Randomized, double-blind trials that compare outcomes of patients taking a drug or placebo, or another drug are considered the "gold standard" of clinical trials, because they can actually show what patients experience.

In contrast, observational studies use data from patient records or other sources to paint a picture of patient outcomes. Since these data are from past experience, the conclusions of these studies can find associations, but not establish causes of outcomes.

The report is published in the Oct. 6 online edition of the New England Journal of Medicine.

For the study, Bhatt and colleagues randomly assigned 3,873 patients who needed Plavix to Plavix alone or in combination with omeprazole (Prilosec) or a placebo; patients also received aspirin.

Over six months, 51 patients had gastrointestinal bleeding. That was a rate of bleeding of 1.1 percent among those taking Plavix plus Prilosec and 2.9 percent among those taking Plavix and a placebo, the researchers found.

In addition, 109 patients had a heart attack, stroke, died or needed another cardiac procedure. The rate of these events was 4.9 percent among those receiving Prilosec and 5.7 percent among those receiving a placebo, Bhatt's group found.

More patients taking Prilosec had a higher risk of diarrhea, the researchers noted.

The study also had two main limitations, the researchers reported: It was terminated early due when the sponsor, Cogentus Pharmaceuticals, lost financing, and the numbers of participants were not large enough to rule out the possibility of a clinically significant difference in cardiovascular events, such as heart attack, due to the use of a PPI.

However, the study did not find any significant increases in the risk of cardiovascular events, even in high-risk group, the researchers reported.

"This should be quite reassuring to physicians that there isn't a bad interaction to worry about," Bhatt said.

Commenting on the study, Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, said that "there have been significant concerns based on observational studies and platelet function testing that proton-pump inhibitors like Prilosec may interfere with the antiplatelet effect of clopidogrel, increasing the risk patients would have cardiovascular events."

"This trial is quite reassuring, with no signal of cardiovascular harm when proton pump inhibitors are given to patients receiving clopidogrel and aspirin," said Fonarow, who was not involved with the study. "Prophylactic use of proton-pump inhibitors may be appropriate in patients at increased risk for gastrointestinal bleeding."

Another expert, Dr. James Brophy, a professor of medicine and epidemiology at the Royal Victoria Hospital in Montreal, said that "much of the problem of earlier research in this area has been observational and therefore subject to potential biases. The present study is a big step forward as it was a randomized study."

This latest finding -- coupled with the fact that other recent studies have not confirmed earlier studies suggesting an increased in adverse cardiac events -- is reassuring, he said.

"For the moment, the data is reassuring that PPIs can be safely prescribed if there is a clinical indication," Brophy said. "The story does seem a prime example of the Proteus phenomena, initially very positive worrisome results generally being proven to be not as extreme as initially feared."

Indeed, a recent Danish study also found that taking Plavix and a PPI together was safe and did not compromise the effects of Plavix.

More information

For more information on the Plavix-PPI combo, visit the U.S. Food and Drug Administration.