December 27th, 2011
06:07 PM ET
The popular blood-thinner Plavix is a safe and effective medication for patients, including those deemed to be "poor metabolizers" of the drug, says an analysis released today in the Journal of the American Medical Association.
The findings contradict the 2010 boxed warning that the Food and Drug Administration mandated be placed on the drug's label.
If you're one of the approximately 40 million people worldwide taking Plavix (known generically as clopidogrel), you're probably familiar with the warning. The label cautions that the drug has "diminished effectiveness in poor metabolizers", or patients with a certain genotype, known as CYP2C19, and thus may lead to an increase in cardiovascular events like heart disease, stroke, or bleeding. To help decide if Plavix is a good fit for patients, the label says genetic tests are available to identify people with the genotype in question.
"The drug Plavix itself is not active, it has to be metabolized in order to become activated," explains Dr. Steven Nissen, with the Department of Cardiovascular Medicine at The Cleveland Clinic. The liver enzyme CYP2C19 is what activates the drug.
"If you're a slow metabolizer theoretically you might not produce enough active drug to get the anti-coagulant effect of Plavix and that's why all of this from a theoretical point of view made sense but the problem is that theory is one thing but reality is another."
Dr. Nissen was not affiliated with the analysis but did write an editorial accompanying its publication. He believes that the FDA jumped the gun in mandating the boxed warning.
"FDA acted prematurely in putting a warning on the drug without the level of evidence that we would consider to be adequate for most standards," says Dr. Nissen.
"They were trying to do the right thing but if you look at it in the most rigorous fashion, it wasn't the right answer and it's now time to rethink it."
Dr. Eric J. Topol, the Chief Academic Officer of Scripps Health and a practicing cardiologist, disagrees with Dr. Nissen and the conclusion of the meta-analysis.
According to Dr. Topol, previous studies have found only that patients with stents would benefit from genetic testing to determine if Plavix is an appropriate drug. He believes the FDA's recommendation for certain patients to be tested for the genotype CYP2C19 remains valid.
"Patients who get stented should have the genotype test to see if they're going to respond," says Dr. Topol, who was also not affiliated with the analysis.
If patients with stents have the gene, and Plavix does not work effectively for them, "they're vulnerable to clotting their stent and if a person clots their stent, they'll either die or have a heart attack," says Dr. Topol.
"You don't want to be walking around with a stent and have this vulnerability."
In a written statement to CNN, a FDA spokesperson said the agency did not have a specific comment on the analysis.
"Generally, we do not provide comments on individual studies, reports or articles. Rather, the FDA collectively reviews the literature and takes such information into account as we discuss drug safety issues and make regulatory decisions."
So what does all this mean for patients? If you're concerned about taking Plavix, talk to your doctor to learn if genetic testing is a good option for you.
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