March 18, 2010 – The U.S. Food and Drug Administration (FDA) today added a boxed warning to the anti-blood clotting drug Plavix (clopidogrel), alerting patients and healthcare professionals that the drug can be less effective in people who cannot metabolize the drug to convert it to its active form.
Plavix reduces the risk of heart attack, unstable angina, stroke, and cardiovascular death in patients with cardiovascular disease by making platelets less likely to form blood clots. Plavix does not have its anti-platelet effects until it is metabolized into its active form by the liver enzyme, CYP2C19.
People who have reduced functioning of their CYP2C19 liver enzyme cannot effectively convert Plavix to its active form. As a result, Plavix may be less effective in altering platelet activity in those people. These “poor metabolizers” may not receive the full benefit of Plavix treatment and may remain at risk for heart attack, stroke, and cardiovascular death.
“We want to highlight this warning to make sure health care professionals use the best information possible to treat their patients,” said Mary Ross Southworth, Ph.D., a clinical analyst in the Division of Cardiovascular and Renal Products in the FDA’s Center for Drug Evaluation and Research.
In May 2009, the FDA added this warning to the drug’s label. After reviewing more data, the agency felt it was important to highlight this risk in a boxed warning.
It is estimated that 2 to 14 percent of the U.S. population are poor metabolizers. The FDA recommends that healthcare professionals consider alternative dosing of Plavix for these patients, or consider using other anti-platelet medications. Tests are available to assess CYP2C19 genotype to determine if a patient is a poor metabolizer.
Patients should not stop taking Plavix unless told to do so by their healthcare professional, and are encouraged to discuss concerns about Plavix with their doctors.
Plavix is made under a Bristol-Myers Squibb/Sanofi-Aventis Pharmaceuticals partnership.
For information:? www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm203888.htm
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July 10, 2024 
