The FDA ( Food and Drug Administration ) has warned to avoid using the stomach acid reducer Omeprazole ( Prilosec ) with the anti-clotting drug Clopidogrel ( Plavix ).
New data suggest that when patients take both Omeprazole and Clopidogrel, Plavix’s ability to block platelet aggregation may be reduced by about half.

Clopidogrel is used to prevent blood clots that could lead to myocardial infarctions or strokes in at-risk patients. Omeprazole is a proton pump inhibitor ( PPI ) used to reduce the production of stomach acid and prevent stomach irritation.

Plavix does not have anti-clotting effects until it is converted or metabolized into its active form with the help of the liver enzyme, CYP2C19. Omeprazole blocks this enzyme, thereby reducing the effectiveness of Clopidogrel.

After issuing an Early Communication in January about possible drug interactions involving Clopidogrel, the FDA requested new studies from the drug’s manufacturers, Sanofi-Aventis and Bristol-Myers-Squibb ( BMS ). These new studies support the existence of a significant interaction that could negatively impact a person’s health. Based on the current scientific information, the Plavix label has been updated with new warnings about the use of Omeprazole and other drugs that inhibit the CYP2C19 enzyme and that could interact with Clopidogrel in the same way.

The new studies compared people who took Clopidogrel and Omeprazole together with people who took Clopidogrel alone. A reduction in Plavix’s anti-clotting effect was found in those individuals who took the combination. Similar results were seen irrespective of whether the two drugs were taken at the same or different times of day.

It is unknown how other PPIs may interfere with Plavix. Other drugs that should not be used with Plavix because they may have a similar interaction with CYP2C19 include Nexium ( Esomeprazole ), Tagamet and Tagamet HB ( Cimetidine ), Diflucan ( Fluconazole ), Nizoral ( Ketoconazole ), Vfend ( Voriconazole ), Intelence ( Etravirine ), Felbatol ( Felbamate ), Prozac, Serafem, Symbyax ( Fluoxetine ), Luvox ( Fluvoxamine ) and Ticlid ( Ticlopidine ).

Zantac ( Ranitidine ), Pepcid ( Famotidine ), Axid ( Nizatidine ), and antacids do not inhibit the CYP2C19 enzyme and aren’t expected to interfere with the anti-clotting activity of Plavix.

Source: FDA, 2009

XagenaMedicine2009


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