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 haloperidol 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 haloperidol 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 haloperidol as compared to patients with alleles that result in a normal metabolizer phenotype. Be aware that the DPWG guideline for haloperidol and CYP2D6 has a 'no recommendation' for intermediate metabolizers. This annotation only covers the pharmacokinetic relationship between CYP2D6 and haloperidol and does not include evidence about clinical outcomes. Other genetic and clinical factors may also influence haloperidol metabolism.