Effects of methadone plus alcohol on cognitive performance in methadone-maintained volunteers

Background: Methadone maintenance patients (MMP) often abuse other drugs, including alcohol. The combined use of methadone and alcohol could impair performance and daily functioning. Objective: To examine the effects of methadone in combination with alcohol, as well as acute increases in methadone, on performance outcomes. Methods: This double-blind, double-dummy, crossover study included eight opioid-dependent participants stabilized on methadone. Participants completed six inpatient sessions corresponding to methadone (100% or 150% of daily dose) and beverage (placebo, 0.25 or 0.50 g/kg alcohol). Performance tasks were completed before and after drug administration. Area under the time-course values were analyzed by a 2 (methadone dose) by 3 (alcohol dose) repeated measures analysis of variance. Results: Main effects of methadone were observed for two attention outcomes, suggesting reduced accuracy and slowed responding at an elevated methadone dose. In addition, main effects of alcohol were observed for episodic memory (false alarms and response bias) suggesting more impulsive responding as alcohol dose increased. No robust interactions of methadone and alcohol were observed for any outcome. Conclusions: Study findings indicate that an acute increase in methadone (150%) and a moderate dose of alcohol (2-3 drinks) can impair distinct aspects of performance, although no significant interactive effect between methadone and alcohol was found. Future studies with larger sample sizes, larger doses, and more clinically informative tasks could expand on the present findings and further explore the cognitive consequences of concurrent opioid and alcohol use.