A Medco Health Solutions study presented Tuesday at the American Heart Association meeting in New Orleans reveals that stent patient taking Sanofi-Aventis/Bristol-Myers Squibb’s blood thinner block buster Plavix or clopidogrel along with certain heartburn drugs such as AstraZeneca PLC's Nexium may face a greater risk of heart attack, stroke and other dangerous events than those who took Plavix alone.

Nexium and other proton pump inhibitors, like Wyeth’s Protonix and Prevacid, Eisai Co.'s Aciphex, are used to treat heartburn, in which stomach acids come back up the esophagus, causing pain and inflammation. The drugs are usually prescribed for patients taking Plavix because the drug has been associated with a higher risk of ulcers.

Nexium was AstraZeneca’s top-selling product, generating revenue of $1.32 billion in the third quarter of 2008. Plavix generated $1.44 billion for Bristol-Myers during the same period.

The researchers at Medco, the largest US drug benefits manager, found that, overall, proton pump inhibitors were associated with a 50 percent increase in the risk of heart attack, stroke, bypass surgery and cardiac-related death for Plavix users. People who took anti-clotting drugs alone had problems a fifth of the time.

“Considering the widespread use of these two medications, this important research adds to a growing body of evidence raising questions about their concurrent use and suggests further research is needed,” said Dr. Robert Epstein, Medco's chief medical officer and the study's lead author.

The study involved 16,690 patients followed for a year who needed a “cardiac intervention” such as a stent or a balloon and went on to take Plavix. Of those, 6,828 also took a proton-pump inhibitor. The study found that about 18 percent in the Plavix-alone group had another cardiac event within a year of the original intervention, while nearly 25 percent of those taking both drugs had another cardiac event.