Plavix, a popular anti-clotting drug, could soon have new information added to its label detailing genetic factors that might inhibit its effectiveness. According to The Wall Street Journal, the Food & Drug Administration (FDA) is considering the changes after various studies showed Plavix failed to work in nearly a third of the cardiac patients who used it.
Plavix is used to prevent blood clots after a recent heart attack or stroke, and in people with certain disorders of the heart or blood vessels. The medication keeps the platelets in the blood from coagulating to prevent unwanted blood clots that can occur with certain heart or blood vessel conditions.
There is no way for doctors to measure how well Plavix is working. Generally, if patients avoid another heart attack or stroke, it is thought to be effective. But according to The Wall Street Journal, medical literature on Plavix has shown heart patients suffered cardiac events even though they were taking the drug regularly, but no one understood why.
According to the Journal report, studies in two studies published in the New England Journal of Medicine and another in Lancet last week identified a genetic abnormality in some heart patients that could interfere with their liver’s ability to completely process Plavix in the bloodstream. Two of the studies suggested the drug was less effective in about 30% of the population, but the third put the risk at only 5%.
That uncertainty is apparently causing problems for the FDA. The Journal said the agency is having trouble deciding just what type of labeling changes to make to Plavix, as well as what guidance should be given to doctors.
Right now, the FDA is thinking about adding a recommendation to Plavix that patients undergo genetic testing before starting it. But for patients with the genetic abnormality, there are no easy answers. According to the Journal, increasing the dosage of Plavix can increase the risk of internal bleeding. Unfortunately, right now there are no alternatives to Plavix available in the U.S.