Health Inc.

FDA Warns Plavix May Be Ineffective In Some People

The Food and Drug Administration slapped its strongest warning on Plavix, a popular pill to prevent blood clots in people with heart disease.

Plavix is most likely to be ineffective in Asians. i i

Plavix is most likely to be ineffective in Asians. (AP Photo/Mark Lennihan) Mark Lennihan/AP hide caption

itoggle caption Mark Lennihan/AP
Plavix is most likely to be ineffective in Asians.

Plavix is most likely to be ineffective in Asians. (AP Photo/Mark Lennihan)

Mark Lennihan/AP

The problem: the drug may not work in some people. To be effective, the medicine inside each Plavix pill first has to be activated by the liver. Turns out the enzyme that does the job isn't up to the task in some people, depending on the variation of a gene they carry.

Research in the past few years has show that's problem is present in about 2 percent of Whites, 4 percent of Blacks, and 14 percent of Chinese.

The fine print in the Plavix instructions for doctors already noted that info, but today the FDA said the evidence for the problem has gotten stronger, so the label needed to be beefed up. Patients can get a genetic test, costing around $500, that will predict how they'll do.

Dr. Louis Teichholz, head of cardiology at Hackensack University Medical Center, told Shots, the warning is important and should be taken into account by doctors and patients, But, he said the testing question remains open. "At this point there isn't enough good scientific data to test everybody." Even among Asians, who have the highest prevalence of the gene, you have to test seven people to find one who might have a problem, he said.

Teichholz prefers a test of platelet aggregation, or stickiness, to the genetic assay. The platelet test is cheaper and may also help flag patients who aren't taking their medicine.

For people who do have trouble metabolizing Plavix, a stronger dose may overcome the problem. A rival drug called Effient may also work.

Last year, the FDA cautioned that patients shouldn't mix Plavix and heartburn pill Prilosec because the combination weakened Plavix's effectiveness.

Correction: The initial version of this post said that Plavix may be ineffective in up to 14 percent of Asians. The 14 percent figure applied to Chinese, not all Asians.

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