Table 1. CYP2C19 phenotypes derived from CYP2C19 genotype.
| Genotype | Phenotype |
|---|---|
| *1/*1 | Normal metabolizer (NM) |
| *2/*2, *2/*3, or other combination of two loss-of-function alleles | Poor metabolizer (PM) |
| *1/*2, *1/*3, *2/*17† or other genotypes with a single loss-of-function allele | Intermediate metabolizer (IM) |
| *1/*17 | Rapid metabolizer (RM) |
| *17/*17 | Ultra-rapid metabolizer (UM) |
†
The IM phenotype assignment for genotypes with one loss-of-function and one gain-of-function allele (e.g. *2/*17) is based on evidence of increased platelet aggregation among clopidogrel treated patients with this genotype compared to the *1/*1 genotype, indicating that that the *17 allele is unable to completely compensate for reduced activity with the *2 allele.29 However, the data are not completely consistent, and thus the IM phenotype assignment is considered provisional.