Missing Liver Enzyme
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IMAGE SOURCE: Plavix Web site
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Plavix is by all counts a blockbuster drug for Bristol-Myers Squibb Co. and Sanofi-Aventis, with sales of more than $8 billion a year.
But the value of the drug slipped today as the FDA announced Plavix will have to carry a black box warning about patients who respond poorly.
The language will “warn about reduced effectiveness in patients who are poor metabolizers of Plavix,” says the FDA on its Web site.
That impacts about 2 to 14 percent of users.
Doctors may be able to use a genetic test to determine who is a poor metabolizer of Plavix. The cost of such tests usually runs about $500, which for many is cost prohibitive.
Plavix keeps blood platelets from sticking together to form a clot, which causes heart attack and stroke.
A poor metabolizer may be someone with low levels of a particular liver enzyme that aids breakdown. When that happens, the individual cannot convert Plavix into its active form effectively.
A patient unable to metabolize the drug, is at an increased risk for heart attack and stroke. Poor metabolizers may be able to use aspirin instead, says the FDA.
What should patients do?
“Patients should not stop taking Plavix unless told to do so by their health care professional,” the agency says. “They should talk with their health care professional if they have any concerns about Plavix, or to find out if they should be tested for being a poor metabolizer.”
This is the second label change for Plavix.
The Detroit Free Press reports that the FDA added similar language to the label in November. This time the warning will appear in a black box which addresses the most serious risk.
Last year, researchers found that patients who used Plavix in combination with heartburn drugs, Nexium, Prevacid, Protonix, and Prilosec OTC were 50 percent more likely to experience a heart attack.
Plavix, the second best-selling drug in the world, loses its patent protection in 2010, reports Reuters.
The black box warning may encourage doctors to turn to the second most popular clot-buster, Effient, by Eli Lilly & Co. #