2010-03-18
The Food and Drug Administration
(FDA) announced a boxed warning to the antiblood clotting drug Plavix
(clopidogrel), alerting patients and health-care 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 antiplatelet 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.
FDA recommends that health-care professionals
should:
- Be aware that some patients may be poor metabolizers of
Plavix. They do not effectively convert Plavix to its active form because
of low CYP 2C19 activity. The effectiveness of Plavix as a preventive
therapy is reduced in these patients.
- Be aware that tests are available to determine
patients' CYP2C19 status.
- Consider use of other antiplatelet medications or
alternative dosing strategies for Plavix in patients who have been
identified as poor metabolizers.
- Be aware that although a higher dose regimen (600 mg
loading dose followed by 150 mg once daily) in poor metabolizers
increases antiplatelet response, an appropriate dose regimen for poor
metabolizers has not been established in a clinical outcome trial.
- Review the newly approved Plavix drug label for
complete information on the use of Plavix
For additional information
about the warning visit the FDA
Drug Safety Communication Web site.
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