People who suffer a heart attack nearly double the risk of having another if they are taking the widely used blood thinner Plavix together with a heartburn drug like Prilosec, researchers said on Tuesday.
Plavix, also known as clopidogrel and made by Sanofi-Aventis SA and Bristol-Myers Squibb Co, and aspirin are often used to thin a patient's blood after a heart attack.
Doctors also may prescribe a proton pump inhibitor, or PPI, such as AstraZeneca Plc's heartburn drug Prilosec to cut the risk of gastrointestinal bleeding from bloodthinners.
A study published in the Journal of the American Medical Association tracked 8,205 U.S. patients who were treated for a heart attack or chest pain known as unstable angina and given Plavix and aspirin.
Two-thirds of these patients also took a PPI, primarily Prilosec, and had almost double the risk of having another heart attack or bout of unstable angina compared to those not taking a PPI, the researchers said.
Dr. Michael Ho of the Denver VA Medical Center, who led the study, said this drug combination may be responsible for thousands of repeat heart attacks.
"Our study highlights a potential interaction between clopidogrel and PPI medication. And it suggests that maybe PPI medication should not just be prescribed routinely or prophylactically in patients who are on aspirin and clopidogrel," Ho said in a telephone interview.
Some doctors urged caution regarding the findings.
"We have to be really careful with this study," said Dr. Kirk Garratt of Lenox Hill Hospital in New York.
"If we stop prescribing PPIs for these patients, we will see more bleeding complications. A big bleed for a patient with significant coronary artery disease could easily prove fatal," Garratt said in a statement.