In detail, loss-of-function polymorphisms of the cytochrome P450 isoenzymes CYP2C9 and CYP2C19, advanced age, diabetes, and concomitant treatment with morphine, calcium channel blockers, or the proton pump inhibitor omeprazole were associated with an attenuated response to clopidogrel therapy. The gene discussed is CYP2C9; the disease is diabetes mellitus.