FDA puts Plavix under safety review

The FDA is putting the anti-clotting drug Plavix under its safety microscope. The question: Whether the second-best-selling drug in the U.S. is less effective in some patients.

Two types of patients may have trouble metabolizing Plavix, hampering its ability to prevent clotting, the Associated Press reports. Patients using certain heartburn medications may get less benefit from the drug because the gastro-meds can neutralize its benefits. And particular gene variations may impede Plavix as well.

Marketed by Bristol-Myers Squibb and Sanofi-Aventis, Plavix posted sales of $7.3 billion in 2007. Its sales are important to both companies; in the fourth quarter, for instance, Plavix revenues drove Bristol's earnings growth.

You'll recall that, back in November, new data showed [1] that patients taking Plavix along with a proton pump inhibitor such as AstraZeneca's Nexium were more likely to be hospitalized for heart attack, stroke or chest pain. Researchers theorized that the PPIs might interfere with a liver enzyme needed to metabolize the clot-buster. Some cardiologists, however, disputed that theory, saying that patients with chronic heartburn may already have other health problems that boost their risk for heart attack and stroke.

Meanwhile, both Bristol and Sanofi are studying whether these meds might interfere with Plavix. They're also looking at genetic variations and their effects. The FDA says it's going to review this data and issue recommendations. In the meantime, patients should continue taking Plavix, the agency said, but docs might think twice before prescribing PPIs to patients already using the blood thinner.

- read the AP story [2]