On March 12, 2010 the U.S. Food and Drug Administration announced that the blockbuster anti-clotting drug Plavix will now carry the agency’s strongest warning. The FDA said that they are requiring the boxed warning to alert patients and health care professionals that Plavix may not be an effective anti-clotting treatment in some patients.
Plavix is intended to treat patients suffering from cardiovascular disease by making platelets less likely to form blood clots. When Plavix works properly it can reduce the risk of heart attack, stroke, unstable angina, and cardiovascular death; however, Plavix may offer very little benefit to some individuals who are unable to metabolize the drug into its active form.
Plavix does not begin to display anti-platlet effects until it is metabolized by the liver enzyme CYP2C19. People who do not have normal functioning of the CYP2C19 liver enzyme do not have the ability to convert Plavix to its active form and therefore platlet altering may be less effective in these patients.
Individuals with reduced functioning of the CYP2C19 are known as poor metabolizers. According to the FDA, it is estimated that between and 2 and 14 percent of the American population are poor metabolizers.
In May of 2009, the FDA added this warning to the Plavix label; however, after further review the agency determined that it was important to highlight the risk leading to the boxed warning that was recently announced.
There are tests available to determine if you may be a poor metabolizer. Patients taking Plavix should not stop taking the medication without first consulting with their physician.