WASHINGTON (AP) -- Federal health officials are investigating whether the blockbuster blood thinner Plavix is less effective in some patients.
The Food and Drug Administration is studying reports that taking certain heartburn medications alongside Plavix decreases the benefits of the drug. The FDA is also investigating whether patients' genetic background can interfere with effectiveness.
Plavix is the second-best-selling drug in the world. It is marketed by Bristol-Myers Squibb Co. and Sanofi-Aventis SA.
The companies have agreed to study the effects of genetic factors or heartburn drugs. The studies will take several months to complete.
Until more information is available, the FDA says patients should continue taking Plavix.