CYP2C19

Cytochrome P450 enzyme that activates clopidogrel (prodrug) and metabolises proton pump inhibitors (omeprazole, lansoprazole), diazepam and sertraline.

CYP2C19 inhibition (e.g. omeprazole + clopidogrel) reduces formation of the active clopidogrel metabolite and may decrease antiplatelet protection; induction (rifampicin) accelerates substrate metabolism.

Classic interaction: omeprazole (or esomeprazole) + clopidogrel reduces antiplatelet efficacy; prefer pantoprazole when a PPI is needed in a patient on clopidogrel.