Pathway involved in the formation of the active and endo metabolites of clopidogrel in patients with polymorphisms in cytochrome P450 family 2 subfamily C member 19 ( CYP2C19) and paraoxonase-1 ( PON1 ).

In carriers of ≥1 PON1 192R allele, high PON1 activity may accelerate an increase in the production of the endo metabolite of clopidogrel. Low CYP2C19 activity in carriers of ≥1 CYP2C19 no function allele may reinforce this cascade via the delayed metabolism of 2-oxo-clopidogrel into an active metabolite, which allows PON1 to metabolize 2-oxo-clopidogrel into the endo metabolite of clopidogrel. GSH, glutathione.