Plavix Black Box Warning Issued: May Not Work in Some Patients

A “Black Box” warning has been placed on the anti-blood clotting drug Plavix, alerting patients and health care professionals that the drug may not work effectively in some patients due to genetics. This could cause serious or life-threatening injuries for individuals given the medication to reduce the risk of heart attack, unstable angina, stroke or cardiovascular death among those with cardiovascular disease.

The FDA announced the Plavix boxed warning warning on Friday, warning doctors that they should consider another anti-clotting drug for patients who are confirmed to be poor metabolizers of Plavix through genetic testing. The FDA said a genetic test is available which will determine whether patients are able to metabolize Plavix efficiently.

The black box warning is the most stringent warning label the FDA can require on a drug.

Plavix (clopidogrel) is a blood thinner that prevents blood platelets from sticking together to form clots. It is a blockbuster medication, generating annual sales of over $6 billion for Bristol Myers Squibb Co. and Sanofi-Aventis.

In August 2009, researchers from the University of Maryland identified a gene variant found in about one-third of the population that may signal a reduced effectiveness of Plavix. The people with the CYP2C19 variant have reduced functioning of a liver enzyme that is supposed to covert Plavix from its inactive form to its active form, potentially making Plavix ineffective at reducing the risk of blood clots.

The genetic variant is found in about 30% of Caucasians and blacks, and up to 60% of Asians. Simple genetic tests using DNA from blood or saliva can identify poor Plavix metabolizers. The tests are estimated to cost about $500, however, identifying poor Plavix metabolizers could prevent patients from being unnecessarily exposed to risk of Plavix side effects, such as an increased risk of gastrointestinal bleeding, ulcers and a possible increase in the risk of heart attacks or strokes for those with high cholesterol or high blood pressure.

Bristol Myers Squibb Co. and Sanofi-Aventis currently face a number of Plavix lawsuits filed by plaintiffs who claim that the drug maker failed to adequately warn about problems associated with use of their drug.