FDA Black Box Warning: For Some Patients Plavix Not Effective
Some patients with a certain genetic variation are not able to metabolize the blood thinning drug Plavix, making them at risk for a heart attack and a stroke. Because of this increased risk, the FDA is requiring that the drug carry a black box warning on its label.
Plavix, generic name clopidogrel, is prescribed after a cardiac even such as a heart attack or stroke or after a procedure to open blocked coronary arteries. It causes the platelets in the blood to be less sticky and less likely to form a dangerous blood clot.
Some patients, called “poor metabolizers”, do not have adequate levels of a liver enzyme called CYP2C19 that is necessary to convert Plavix into an active form for antiplatelet action. Asians are at the greatest risk – about 14% lack the enzyme. Four percent of African Americans are at poor metabolizers and two percent of whites are low in the enzyme activity.
In May 2009, the FDA required that a warning statement be placed on the Plavix label, but has recently decided the information must be more prominent, thus requiring the “black box”, the FDA’s strongest warning.
The FDA warns that patients should not stop taking Plavix without first consulting with their doctor. A simple, but expensive test is available to assess the presence or absence of the CYP2C19 genotype. Doctors may opt to place poor metabolizers on higher than usual doses or may switch patients to another type of anti-clotting drug, including Ticlid (ticlopidine) or Efient (prasugrel).
Plavix is made in partnership by two pharmaceutical companies, Bristol-Myers Squibb and Sanofi Pharmaceuticals. The new labeling should be added to Plavix during the next two months.
Consumers who have adverse reactions to Plavix or any other medication should contact the FDA by phone at 1-800-FDA-1088, fax at 1-800-FDA-0178, online at http://www.fda.gov/medwatch, or by mail to 5600 Fishers Lane, Rockville MD 20852-9787