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



There is another, simpler non-invasive test that can be performed to determine a patient's rsponse to Plavix. It measures endothelial function and is called an EndoPAT test (Itamar Medical). A recent article in the American Journal of Cardiology (2/1/10) discussed a study that examined patients' endothelial function following PCI and their response to clopidogrel (Plavix). It concluded that there is a relationship between impaired endothelial function and platelet reactivity. The EndoPAT test takes 15 minutes and is reimbursed by major carriers. This test is the only FDA approved endothelial function test and provides the earliest clinically detectable stage of CV.
I'm a 60 yo Anglo male. I recently had 3 stents place in my heart. While in the hospital I requested the enzyme test for Plavix due to the fact that I don't metabolize Claritin at all. And, as my doctor says, if anything can be odd, it will be so with me. The hospital blew me off. After taking Plavix for a week I cut my hand in a couple of spots and it didn't bleed any more than a slight seep. I contacted my insurance and was told to call the hospital to find out about getting the test. After a bit of runaround they finally said if I wanted the test I could have it. I spoke with my primary doctor and he said get it. The next morning I was getting my blood drawn while a special courier waited for the vials of blood because in has to be kept at room temp and have the test run within two hours of the draw. I didn't even bleed when the needle was removed. Six hours later I was informed to stop taking Plavix and that the hospital was faxing a prescription for Effient to my pharmacy. I called to make sure they had some (of course not) but they did locate another pharmacy that could provide some. I still don't bleed much if cut but it's much more than with the Plavix. At the heart center they claim I'm one of two out of 10,000 patients there. Aren't I lucky?