Plavix Gets Black Box Warning

The FDA has warned that Plavix may not work for some people, putting them at greater risk for heart attack and stroke. The blood-thinner (anti-clotting) drug will get a black box warning and doctors have been told to consider alternative medications--such as aspirin-- for patients who cannot process the drug.

According to a report from the FDA, some patients with a genetic variation cannot metabolize the drug—meaning their bodies don't effectively convert Plavix to its active form. An estimated 2 percent to 14 percent of the population are poor metabolizers of Plavix. Patients can determine if they don't respond to Plavix by taking a genetic test.

The $8-billion-a-year drug sold by Bristol-Myers Squibb and Sanofi-Aventis makes Plavix the second-best selling drug in the world.