Table 2.

Expected effects of CYP2C19 polymorphism on clopidogrel metabolism

Genotype	Expected effect on clopidogrel metabolism
CYP2C19*1/*1	Normal metabolizer—the subject is expected to demonstrate effective antiplatelet response to a standard dose of clopidogrel
CYP2C19*1/*2	Intermediate metabolizer—the subject exhibits approximately half-normal enzyme activity, thus an increased dosage of clopidogrel or an alternative treatment should be considered
CYP2C19*1/*3
CYP2C19*1/*4
CYP2C19*1/*5
CYP2C19*2/*17	Normal/intermediate metabolizer—the subject is likely to have metabolic activity between normal and intermediate metabolizers. In general, the response to a standard dose of clopidogrel should be sufficient
CYP2C19*3/*17
CYP2C19*4/*17
CYP2C19*5/*17
CYP2C19*2/*2	Poor metabolizer—the subject is characterized by a greatly decreased enzyme activity and may require an alternative treatment or higher than standard dosage of clopidogrel to achieve required antiplatelet effect
CYP2C19*2/*3
CYP2C19*2/*4
CYP2C19*2/*5
Or other configuration of these alleles
CYP2C19*1/*17	Rapid metabolizer—the subject have elevated enzyme activity and may be exposed to a higher concentration of active drug metabolites resulting in increased bleeding risk
CYP2C19*17/*17	Ultra rapid metabolizer—the subject have markedly elevated enzyme activity. For prodrugs, like clopidogrel, ultra rapid metabolizers are exposed to a higher concentration of active drug metabolites and may require lower than standard dosage because of increased risk of bleeding