The blockbuster anti-clotting drug Plavix will carry a new warning about patients who have a poor response to the drug because they do not break it down well.
The Food and Drug Administration said it was adding a new boxed warning to Plavix, an $8-billion-a-year drug. Poor metabolizers are people whose bodies do not effectively convert Plavix to its active form.
Plavix is the second-best selling drug in the world. It loses patent protection in 2012.