Role of CYP3A5 in abnormal clearance of methadone.

Objective: To report a case of unusually low concentrations of methadone in a polydrug abuser during maintenance treatment with methadone.

Case Summary: A 25-year-old man (weight 55 kg, height 165 cm) with a 12-year history of polydrug abuse was admitted to an opiates withdrawal methadone program. At the time of our observation, he was using both cannabinoids and heroin; no other medical conditions were discovered.