Effects of methadone on cognition, mood and craving in detoxifying opiate addicts: a dose-response study

RATIONALE: Methadone is the most widespread pharmacological treatment for opiate dependency but relatively little is known of its effects on cognitive and psychomotor functioning, drug craving and mood. Objective: The present study aimed to assess the acute effects of methadone in patients admitted to an opiate detoxification programme. METHODS: Patients were randomly allocated to one of two groups who received either 50% or 100% of their daily stabilisation dose, and a placebo, in a double-blind, cross-over design. Twenty patients completed the study, all were assessed pre- and post-drug on 2 separate testing days. RESULTS: Performance on a task tapping episodic memory (delayed recall of a prose passage) was significantly impaired following the 100% daily dose of methadone. Methadone treatment had no effect on craving or mood. Patients were unable to distinguish between methadone and placebo treatments. CONCLUSIONS: A single dose of methadone can induce episodic memory impairment in patients who have a history of heroin use averaging more than 10 years. Such impairment can be avoided by giving methadone in divided doses.