The Food and Drug Administration said it has ordered the makers of the widely used blood thinner Plavix to conduct studies into the possible interaction of the drug with a class of acid-reflux medicines, known as proton pump inhibitors. The FDA is working with Sanofi-Aventis SA and Bristol-Myers Squibb to determine the reasons behind the so-called clopidogrel resistance phenomenon.

 

Proton pump inhibitors, such as the prescription drugs Nexium, Prevacid, Aciphex and Protonix. Prilosec, are effective in reducing the adverse reactions of Plavix by suppressing the production of stomach acid.

 

The agency advised patients who take Plavix and these types of inhibitors to discuss the combination with their physician. Doctors should also reevaluate the use of some heartburn drugs, including over-the-counter versions, in patients taking Plavix, the FDA said in a statement on its website.

 

Plavix, the world's second-best selling drug, generated revenue of $7.3 billion in 2007. More than 90 million patients around the world have taken the drug to reduce the risk of blood clots that may lead to heart attacks and strokes.

 

A major study conducted by Medco, which looked at almost 17,000 patient benefit records, has found a 74% increase in heart attacks in patients taking both Plavix and PPIs together.

At the same time, a study published last year in the Journal of the American Medical Association has shown that patients suffering from acute coronary syndrome who stop taking clopidogrel (Plavix) may be more likely to die or to suffer an acute myocardial infarction especially in the first 90 days after cessation.