Plasma methadone measurements and their role in methadone detoxification programs.

We monitored eight patients who were receiving a decreasing dose of methadone for treatment for opioid addiction (detoxification). Patients with plasma concentrations of methadone less than 0.05 mg/L experienced withdrawal symptoms, relapsed, and re-abused illicit drugs. Four patients took extra methadone (illicitly obtained) during detoxification. None of the eight patients in our study were successfully weaned off methadone: all left the methadone detoxification program before the completion of treatment. Two patients subsequently returned to a fixed methadone program elsewhere, and four relapsed and returned to illicit drug misuse. Plasma measurements may help clinicians assess patients during methadone detoxification.