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May 2010 Issue

In March, the U.S. Food and Drug Administration added a boxed warning to Plavix alerting people that the drug can be less effective in users who cannot metabolize the drug and convert it into its active form.
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Concern Still Prevalent Among Users of Popular Anti-Clotting Medication

By Katie Pence
Published May 2010

In mid-March, the U.S. Food and Drug Administration added a warning label to the box of the anti-clotting drug Plavix, letting both patients and health professionals know that the drug can be less effective in people who cannot metabolize it correctly to ­­make it active in the body.

Since then, UC Health cardiologists have seen many patients who are frightened by the warning, but experts say it only affects a small percentage of the population.

Plavix, the brand name for Clopidogrel, reduces the risk of heart attack, stroke and cardiovascular death in patients with cardiovascular disease by making platelets less likely to form blood clots.

It does not have its anti-platelet effects until it is metabolized into its active form by the liver enzyme CYP2C19.

It is marketed by Bristol-Myers Squibb and Sanofi-Aventis Pharmaceuticals.

"Without this important enzyme, patients will essentially be taking a placebo, with no effect on their cardiovascular health,” says Massoud Leesar, MD, UC Health interventional cardiologist.

"We’re taking this new development seriously, but we want patients to know that it doesn’t apply to everyone and that the drug has been proven to be beneficial to many.”

According to reports, people of Chinese descent may have up to a 14 percent incidence of having impaired CYP2C19 enzyme activity.

For blacks, it is about 1 in 25, and for Caucasians the incidence drops to 1 in 50.

Testing for the impairment can cost $500 or more; however, with this recent discovery, widespread testing could lower the cost.

For now, Leesar says patients and doctors are considering their choices, and patients should not stop taking their Plavix without advice from their physician.

"Patients should consult their doctor if they have questions, but I urge the general population to continue to take the medication that was prescribed to them until further notice,” he says.

"Otherwise, they could be putting themselves in harm’s way.”

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