Additional methadone increases craving for heroin: a double-blind, placebo-controlled study of chronic opiate users receiving methadone substitution treatment.

AIMS To assess the acute-on-chronic effects of methadone on drug craving, mood and cognitive and psychomotor functioning in patients on long-term methadone substitution treatment. DESIGN AND PARTICIPANTS A double-blind, cross-over design was used to compare the effects of a 33% increase in patient's daily dosage of methadone with a matched placebo linctus. Eighteen patients completed the study; all were assessed pre- and post-drug on two separate testing days. FINDINGS Methadone significantly increased both positive craving (expected positive effects) and negative craving (expected relief of withdrawal discomfort) for heroin. Patients were unable to distinguish between methadone and placebo treatments. No differences between treatments emerged in cognitive or psychomotor effects. In terms of mood, patients were more alert and more contented following placebo than following methadone. CONCLUSIONS Additional methadone may "prime" cravings for heroin in methadone substitution patients.