Table 1.

CYP2D64 major phenotype classes and two subclasses [4,7]^a.

Predicted Drug Metabolizing Phenotypeb	Combination of Alleles
UM	A combination of one normal activity allele with one increased activity allele
EM	Two normal activity alleles; a combination of one increased activity allele with one decreased activity allele
IM to EM	A combination of one normal activity allele with one decreased activity allele; a combination of one increased activity allele with one null activity allele
IM	One normal activity allele with one null activity allele; two decreased activity alleles
PM to IM	A combination of one decreased activity allele with one null activity allele
PM	Only null activity alleles detected

^aThe phenotypes were derived from the Human Cytochrome P450 (CYP) Allele Nomenclature Committee website [4] and the PharmGKB website for the related Clinical Pharmacogenetics Implementation Consortium guidelines for CYP2D6 [7].

^bUM: ultrarapid metabolizer; EM: extensive metabolizer; IM: intermediate metabolizer; PM: poor metabolizer.