The anti-clotting drug Plavix is prescribed to just about everyone who's had a heart attack or received a stent. But now, researchers from the Denver VA Medical Center have identified a new and serious interaction between Plavix and anti-ulcer drugs called proton pump inhibitors, or PPIs.
The study looked at the records of more than 8,200 patients who had taken Plavix after a heart attack or heart procedure. About 60 percent had taken a proton pump inhibitor, usually Prilosec or Aciphex.
The anti-ulcer drugs are prescribed because Plavix can irritate the stomach.
But the combination may be risky. As the researchers report in the Journal of the American Medical Association, using Plavix plus one of the proton pump inhibitors raised the likelihood of returning to the hospital with more heart problems, or death from any cause, by about 25 percent.
The researchers, led by Dr. Michael Ho, say it appears that the anti-ulcer drugs interfere with the way Plavix reduces blood clotting, making it more likely that clots will form and heart problems will return.
Dr. Steven Nissen, chief of cardiovascular medicine at the Cleveland Clinic, says the risk is a concern. "When you have an interaction where one drug actually blocks the effectiveness of another drug that treats a serious disorder, you've got to take that seriously." He says hundreds of thousands, if not millions of people are on both drugs.
"Patients and physicians should reconsider why PPIs were prescribed in the first place," says Ho. "If the patients were having no stomach problems, they should use a different medicine, not a PPI."
Ho says his study highlights the importance of post-market surveillance — continuing to study a drug after it goes on the market. Often drugs are tested on relatively healthy people who aren't taking other, possibly interfering medications, and problems may only show up once the drug is being used by the general public.
Earlier this year, the Food and Drug Administration considered the possibility that PPIs might interfere with Plavix and recommended that health care providers think carefully before prescribing the two drugs together. The agency said health care providers should continue to prescribe Plavix because of its proven effectiveness in preventing blood clots that can lead to heart attacks and stroke.
Meanwhile, the FDA is considering whether to approve another drug, similar but not identical to Plavix, that prevents blood clotting. The decision could come within weeks or months. But it's not known whether PPIs interfere with that drug, too.