Patients carrying the CYP2D6*1 allele in combination with an increased function allele may have increased methadone dose requirements as compared to patients carrying two normal function alleles or two no function alleles. However, conflicting evidence has been reported. This drug-variant pair has been assigned a 鈥渘o recommendation鈥?by CPIC, as it was determined to be not clinically actionable. Other genetic and clinical factors may also affect methadone dose requirements.