Race is a factor in the occurrence of CYP2D6 variability.
This variability is accounted for by the differences in the prevalence of various CYP2D6 alleles among the populations-approximately 10% of whites are intermediate metabolizers, due to decreased CYP2D6 function, because they appear to have the non-functional CYP2D6*4 allele,[REF] while approximately 50% of Asians possess the decreased functioning CYP2D6*10 allele [REF].