The U.S. Food and Drug Administration said Tuesday its new data show that omeprazole, or Prilosec/Prilosec OTC, used to reduce stomach acid, interferes with the anti-blood clotting effect of clopidogrel, or Plavix. The agency added that patients at risk for heart attacks or strokes who use clopidogrel to prevent blood clots would not get the full effect of this medicine if they are also taking omeprazole.
As clopidogrel may cause bleeding in the stomach, omeprazole is often used in combination to reduce the production of stomach acid to prevent bleeding. Omeprazole is available by prescription and as an over-the-counter medication to treat frequent heartburn.
Plavix is marketed by Bristol-Myers Squibb (BMY) and Sanofi-Aventis (SNY). Bristol-Myers said last month that third-quarter Plavix sales increased 8% to $1.554 billion. It is the world's second best-selling drug.
According to the FDA's data, omeprazole lowers the anti-blood clotting effect of clopidogrel by almost half when a patient takes these two medicines by blocking the conversion of clopidogrel into its active form. This effect is called a drug interaction.
The FDA has said that patients using clopidogrel should consult with their healthcare provider if they are currently taking or considering taking omeprazole, including Prilosec OTC.
Users of clopidogrel who need to reduce stomach acid can use antacids such as Maalox or Mylanta and most acid reducers like Zantac, Pepcid and Axid, FDA said, adding that the regulator does not believe that these medicines will interfere with the anti-clotting activity of clopidogrel. However, Tagamet and Tagamet HB should not be used.
The FDA further said that the manufacturers of clopidogrel have agreed to look at other possible drug interactions with the medicine. Also, the clopidogrel label will be updated with new warnings on omeprazole and other drugs that could interact with it in the same way.
BMY closed Tuesday's regular trade at $24.23, down $0.07 or 0.29%, on 24.81 million shares.
SNY ended the regular trade on Tuesday at $38.47, down $0.47 or 1.21%, on 929,406 shares.
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June 05, 2026 16:18 ET A busy week for economic news flow saw a slew of reports being released that reflected the trends in the U.S. labor market. In Europe, economic growth and inflation data gained attention as the European Central Bank and Bank of England head for policy session later in the month. In Asia, the monetary policy session of the Indian central bank was in focus as the country, a major oil importer, reels under the pressures of a weaker rupee and rising inflation.