Clopidogrel (Plavix), which prevents arterial thrombosis by inhibiting platelet activation, is commonly prescribed (usually with aspirin) for months after acute coronary syndromes and stent implantation.1 It may also, however, increase the risk of bleeding.2 Therefore, a proton pump inhibitor (PPI) such as omeprazole (Prilosec, and others) is often given concurrently to decrease the risk of gastrointestinal (GI) bleeding.2 Some reports have suggested that omeprazole may interfere with the antiplatelet effect of clopidogrel.

PHARMACOKINETICS — Clopidogrel is a prodrug that is activated by CYP450 enzymes in the liver, principally (it is thought) by CYP2C19. Omeprazole is a strong inhibitor of CYP2C19, but all PPIs may inhibit CYP2C19 to some extent.3 Patients who are carriers of CYP2C19 loss-of-function polymorphisms ... more      

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