Methadone plasma levels and persistent drug abuse in high dose maintenance patients.

Methadone maintenance patients who maintained on a high daily dose were divided into good performers and poor performers based on whether they demonstrated persistent use of heroin, non-prescription diazepam, and/or excessive alcohol consumption. Mean methadone plasma levels 24 hours after an oral dose of 80 mg were found to be 410.4 ng/ml in good performers compared to 101.8 ng/ml in poor performers (P less than .05). Seven of nine (77.8%) poor compared to two of 15 (13.3%) good performers had 24-hour methadone plasma levels under 50 ng/ml (P less than .01). High dose methadone patients who show evidence of persistent drug or alcohol abuse should have their 24-hour methadone plasma level determined to help assess whether the patient should receive more methadone or find an alternative treatment.