Table 2.

Assignment of likely CYP2C9 Phenotype based on Genotype (CPIC, 2014)

Likely phenotypeaGenotypeExamples of diplotypes
Ultrarapid metabolizer
(increased activity)
(frequency unknown)		Unknown – currently there are no known increased activity allelesUnknown
Normal metabolizer
(normal activity)
(approximately 91% of individuals)		An individual with 2 normal-function alleles*1/*1
Intermediate metabolizer
(heterozygote or intermediate activity)
(approximately 8% of individuals)b		An individual with one normal-function allele plus one decreased-function allele*1/*3, *1/*2
Poor metabolizer
(homozygous variant, low or deficient activity)
(approximately 1% of individuals)		An individual with 2 decreased function alleles*2/*2, *3/*3, *2/*3

Note: There are no known cases of CYP2C9 ultrarapid metabolizers

a

Global frequencies are approximate. Because haplotype frequencies vary considerably among popualations, please see (8) for individual population frequencies.

b

The enzyme activity in this grouping varies widely. Please see (8) for activity ranges.

This table is adapted from (8). Note: The nomenclature used in this table reflects the standardized pharmacogenetic terms proposed by CPIC (9).

From: Piroxicam Therapy and CYP2C9 Genotype

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Pratt VM, Scott SA, Pirmohamed M, et al., editors.
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