Patients carrying the CYP2D6*6 allele in combination with another no function allele may have decreased methadone dose requirements as compared to patients carrying a normal function allele in combination with a no function allele. 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.