Table 2.

Five of CYP2C19 phenotypes in clopidogrel metabolism based on genotypes.

Phenotype	Examples of diplotypes
Ultrarapid metabolizer (UM)	*17/*17
Increased enzyme activity compared to RM
Rapid metabolizer (RM)	*1/*17
Increased enzyme activity compared to NM but less than UM
Normal metabolizer (NM)	*1/*1
Fully functional enzyme activity
Intermediate metabolizer (IM)†	*1/*2, *1/*3, *2/*17
Decreased enzyme activity
Poor metabolizer (PM)	*2/*2, *2/*3, *3/*3 or other combination of two LOF alleles (*2–*8)
Little to no enzyme activity

^†An individual carrying one functional allele (*1) plus one LOF allele (*2–*8) or one LOF allele (*2–*8) plus one increased-activity allele (*17). It seems that *17 allele is unable to completely compensate for reduced activity with the *2 allele, so *2/*17 is classified to IM.