The blood thinner, Plavix, has received the strongest warning from the Food and Drug Administration, a black warning, citing that some patients may not be able to process the drug. In a statement released Friday, March, 12, 2010, the FDA said "that certain patients with a genetic variation cannot metabolize the drug, putting them at increased risk for heart attack and stroke." A genetic test can be preformed to determine whether or not a patient has a genetic variation that will not allow their body to metabolize Plavix. If patients cannot metabolize Plavix, the FDA recommends that these patients switch to blood thinners that they can metabolize.
According to the FDA between 2 and 14 percent of Americans have low levels of a liver enzyme required to metabolize Plavix. Race is a factor in determining the likelihood of an individual having low levels of the required enzyme for the processing of Plavix. Poor metabolizers make up about 3 percent of the total population who have low levels of the specific liver enzyme. "According to Sanofi-Aventis and Bristol-Myers Squibb, which marker the drug, patients who are designated as poor metabolizers represent about 2 percent of white, 4 percent of blacks and 14 percent of Chinese, according to the prescribing information."
The FDA statement reads, "patients should not stop taking Plavix unless told to do so by their health care professional." The statement continued, "they [patients] should talk with their health care professional if they have any concerns about Plavix, or to find out if they should be tested for a poor metabolizer." Genetic testing can cost around $500.
The new Plavix label also states that using a higher dose of Plavix can assist non-responsive patients to increase blood thinning, this has not be approved by the FDA. In addition, the FDA warned that using Plavix with stomach-soothing drugs, Prilosec and Nexium, can reduce the effectiveness of the drug by half.