Heartburn drugs harm effectiveness of Plavix-study

CHICAGO, Nov 11 (Reuters) - Popular heartburn drugs increase the risk of heart attack or stroke when taken together with the widely prescribed blood thinner Plavix, according to a study released on Tuesday.

Patients taking proton pump inhibitors such as Nexium or Prilosec had a 50 percent higher risk of a major cardiovascular event when also taking clopidogrel, the active ingredient in Bristol-Myers Squibb Co's (BMY.N) blood clot preventer Plavix, according to the study by pharmacy benefit manager Medco Health Solutions Inc (MHS.N).

Proton pump inhibitors limit the effectiveness of clopidogrel, the number two prescription drug in the world, thus increasing the risk of a major cardiac event such as heart attacks and strokes, the Medco researchers said.

Twenty-five percent of patients taking both medications together experienced a major cardiovascular event within 12 months of starting clopidogrel, the researchers said.

"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.

In addition to AstraZeneca Plc's (AZN.L) Nexium and Prilosec, other proton pump inhibitors include Wyeth's (WYE.N) Protonix and Eisai Inc's (4523.T) Aciphex.

The researchers tracked 16,690 patients who had undergone a percutaneous coronary intervention such as stent placement or balloon angioplasty and then started taking clopidogrel as an anti-clotting therapy. (Reporting by Susan Kelly; Editing by Bernard Orr)