The FDA has notified healthcare professionals in the US of new data concerning an interaction between clopidogrel (Plavix®) and omeprazole (Prilosec/Prilosec OTC), showing that when these drugs are co-administered, the effectiveness of clopidogrel is reduced.

In addition to a MedWatch alert, the FDA has issued a Public Health Advisory, Information for Healthcare Professionals, and a follow-up to its previous Early Communication (January 2009) regarding this interaction (all are available to view via the link below).

The FDA highlights the following considerations for healthcare professionals:

• The concomitant use of omeprazole and clopidogrel should be avoided because of the effect on clopidogrel's active metabolite levels and anti-clotting activity. Patients at risk for heart attacks or strokes, who are given clopidogrel to prevent blood clots, may not get the full protective anti-clotting effect if they also take prescription omeprazole or the OTC form.
• Separating the dose of clopidogrel and omeprazole in time will not reduce this drug interaction.
• Other drugs that should be avoided in combination with clopidogrel because they may have a similar interaction include: esomeprazole, cimetidine, fluconazole, ketoconazole, voriconazole, etravirine, felbamate, fluoxetine, fluvoxamine, and ticlopidine.
• At this time the FDA does not have sufficient information about drug interactions between clopidogrel and PPIs other than omeprazole and esomeprazole to make specific recommendations about their co-administration. Healthcare professionals and patients should consider all treatment options carefully before beginning therapy.
• There is no evidence that other drugs that reduce stomach acid, such as most H2 blockers ranitidine, famotidine, nizatidine, except cimetidine (a CYP2C19 inhibitor) or antacids interfere with the anti-clotting activity of clopidogrel. Ranitidine and famotidine are available by prescription and OTC to relieve and prevent heartburn and antacids are available OTC to relieve heartburn.
• Talk with your patients about the OTC medicines they take. Be aware that patients may be taking non prescription forms omeprazole and cimetidine.

This interaction featured in the July 2009 issue of Drug Safety Update (please see link below).