FDA officials said new data suggests when patients take both Prilosec (omeprazole) and Plavix (clopidogrel), Plavix's ability to block platelet aggregation, its anti-clotting effect, might be reduced by about half.
Plavix is used to prevent blood clots that could lead to heart attacks or strokes in at-risk patients, the FDA said. Omeprazole, the active ingredient of Prilosec, is a proton pump inhibitor used to reduce the production of stomach acid and prevent stomach irritation.
The FDA said Plavix does not have anti-clotting effects until it is converted or metabolized into its active form with the help of a liver enzyme. Prilosec blocks that enzyme, thereby reducing the effectiveness of Plavix.
Officials said it's not known how other medications might interfere with Plavix. But the FDA said other drugs that should not be used with Plavix include Nexium, Tagamet, Diflucan, Nizoral, VFEND, Intelence, Felbatol, Prozac, Serafem, Symbyax, Luvox and Ticlid.
Conversely, the FDA said Zantac, Pepcid, Axid and antacids are not expected to interfere with the anti-clotting activity of Plavix.