clopidogrel and omeprazole

Omeprazole inhibits the hepatic enzyme CYP2C19. Clopidogrel is a prodrug that requires activation by CYP2C19 to form its active metabolite, which irreversibly inhibits the platelet P2Y12 receptor. By reducing CYP2C19 activity, omeprazole decreases the formation of clopidogrel's active metabolite and thereby its antiplatelet effect.

Concomitant use leads to reduced platelet inhibition, which may increase the risk of adverse cardiovascular events such as stent thrombosis, myocardial infarction, and stroke. The interaction is clinically relevant, particularly in patients with acute coronary syndromes or those undergoing percutaneous coronary intervention.

Avoid the combination. If gastroprotection is required, consider an H2-receptor antagonist such as famotidine or a proton pump inhibitor with less CYP2C19 inhibition, such as pantoprazole. If omeprazole is considered necessary, weigh the risk of reduced clopidogrel efficacy and monitor for signs of thrombotic events, but no reliable laboratory measure exists to adjust therapy.

Well established. The interaction is documented in the US prescribing information for clopidogrel, which warns against concomitant use of omeprazole. Pharmacokinetic studies show a significant reduction in active metabolite exposure and platelet inhibition. Clinical outcome data support an increased risk of cardiovascular events.