Table 2.

Definition of CYP2C19 metabolizer phenotype.

Allele1	Genotype	Allele activity	Metabolizer phenotype	Frequency (pan-ethnic cohort) [33]
*1/*1	Wild type (WT)	2 active alleles	Normal	41%
			Metabolizer (NM)
*1/*n	Heterozygous WT	1 active allele	Intermediate	21%
		1 inactive allele	Metabolizer (IM)
*2/*2 or *n/*n	Homozygous mutant	2 inactive alleles	Poor	3%
			Metabolizer (PM)
*1/*17	Heterozygous WT	1 active allele	Extensive	24%
		1 increased activity allele	Metabolizer (EM)
*17/*17	Homozygous mutant	2 increased activity alleles	Ultrarapid	4%
			Metabolizer (UM)
*2/*17	Heterozygous mutant	1 inactive allele	Normal metabolizer (NM)	6%
		1 increased activity allele

1 - *2, *3, *8, or *9 refer to loss-of-function (inactive) alleles; n – refers to any of the loss-of-function alleles.