The CYP2D6*10 allele has been assigned as a decreased function allele with an activity value of 0.25 by CPIC. Patients carrying the *10 allele in combination with a decreased or no function allele may have decreased metabolism of aripiprazole as compared to patients with alleles that result in a normal metabolizer phenotype, while patients carrying the *10 allele in combination with an increased function allele with an activity value of 2 may have similar metabolism of aripiprazole as compared to patients with alleles that result in a normal metabolizer phenotype. Patients carrying the *10 allele in combination with an increased function allele with an activity value of 3 or greater may have increased metabolism of aripiprazole as compared to patients with alleles that result in a normal metabolizer phenotype. Be aware that the DPWG guideline for aripiprazole and CYP2D6 has a 'no recommendation' for CYP2D6 ultrarapid and intermediate metabolizers. Other genetic and clinical factors may also influence aripiprazole metabolism. This annotation only covers the pharmacokinetic relationship between CYP2D6 and aripiprazole and does not include evidence about clinical outcomes.