Plavix Heart Attack Risks Are in Our Genes, New Study Finds

A specific gene variation carried by between 30 and 60 percent of people makes some of us more than twice as likely as others to suffer a heart attack or stroke while taking the blockbuster anti-blood clotting drug Plavix, a new study reveals.

The research conducted by the National Institutes of Health and set to be published in an upcoming issue of the Journal of the American Medical Association could give doctors a key screening test to determine who should and should not be given Plavix.

Plavix, known chemically as clopidogrel, is a Bristol-Myers Squibb Co. and Sanofi Aventis SA product that is among the world’s top-selling drugs. It has long been linked to potentially fatal cardiovascular complications and increased risks of severe internal bleeding.

The Food and Drug Administration is now reviewing the safety of Plavix, which some studies have suggested is no better than common heartburn drugs but carries much more risks. Plavix is commonly prescribed to patients who have had a heart attack or stroke or who carry artery-opening stents.

Study Finds Genetic Link to Problems

Researchers studied 429 healthy Amish people and 227 others who had undergone surgeries to open clogged arteries. Volunteers took Plavix for seven days and then were examined to see how their blood platelets responded. Researchers also looked for common gene variations in the group.

They found that patients with a particularly gene variation – called CYP2C19 — were 2.4 times more likely to suffer a heart attack or die when compared to patients without that variation, according to a Reuters News report.

While researchers are not exactly sure why the gene variation hampers the work of Plavix, they said it appears likely that the variant prevents the work of an enzyme that is needed to activate Plavix in the body.

Researcher Dr. Alan Shuldiner of the University of Maryland School of Medicine called the presence of the gene variation “a strong predictor of response to clopidogrel or Plavix.”

People who carry the variation do not convert Plavix from its inactive form to its active form, and therefore are less responsive to clopidogrel, according to Shuldiner.

The research findings could mean that more doctors will screen patients for the gene variant before prescribing Plavix. Doing so could place a red flag on those who are at increased risk of heart attack, stroke, or death before the problems occur.

Gene Variant More Common in Asians

While the gene variation is found in about one in three blacks and Caucasians, it is much more common among Asians, with as many as 60 percent of that population carrying the gene, researchers said.

People with the gene variation may need to take a higher dose of Plavix to overcome the deficiency or be switched to another, more expensive drug, such as Effient (prasugrel).

Generic versions of Plavix are expected to appear on pharmacy shelves in 2011, when Plavix loses its exclusive patent protection.

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