TABLE 1.
ASSIGNMENT OF LIKELY CYP2D6 PHENOTYPES BASED ON DIPLOTYPES
| Likely phenotype | Activity Score |
Genotypesa | Examples of CYP2D6 diplotypes |
|---|---|---|---|
| CYP2D6 ultrarapid metabolizer (~1–2% of patients)b |
> 2.0 | An individual carrying duplications of functional alleles |
*1/*1xN, *1/*2xN, *2/*2xNc |
| CYP2D6 normal metabolizer (~77–92% of patients) |
2.0-1.0d | An individual carrying two normal function alleles or two decreased function alleles or one normal function and one no function allele or one normal function and one decreased function allele or combinations of duplicated alleles that result in an activity score of 1.0 –2.0. |
*1/*1, *1/*2, *1/*4, *1/*5, *1/*9, *1/*41, *2/*2,*41/*41 |
| CYP2D6 intermediate metabolizer (~2–11% of patients) |
0.5 | An individual carrying one decreased function and one no function allele |
*4/*10,*4/*41, *5/*9 |
| CYP2D6 poor metabolizer (~5–10% of patients) |
0 | An individual carrying only no functional alleles |
*3/*4,*4/*4, *5/*5, *5/*6 |
a
Assignment of allele function and citations for allele function can be found https://www.pharmgkb.org/page/cyp2d6RefMaterials (CYP2D6 Allele Definition Table and CYP2D6 Allele Functionality References Table (1)).
b
See the CYP2D6 Frequency Table (1) for race-specific allele and phenotype frequencies or see Gaedigk et al (30).
c
WherexN represents the number of CYP2D6 gene copies. For individuals with CYP2D6 duplications or multiplications, see supplemental data for additional information on how to translate diplotypes into phenotypes.
d
Patients with an activity score of 1.0 may be classified as intermediate metabolizers by some reference laboratories.