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 an drug craving, mood and cognitive and psychomotor functioning in patients on long-term met hadone substitution treatment. Design and participants. A double-blind, cro ss-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 patie nts completed the study; all were assessed pre- and post-drug on two separa te testing days. Findings. Methadone significantly increased both positive craving (expected positive effects) and negative craving (expected relief o f withdrawal discomfort) for heroin. Patients were unable to distinguish be tween methadone and placebo treatments. No differences between treatments e merged in cognitive or psychomotor effects. In terms of mood, patients were more alerts and more contented following placebo than following methadone. Conclusions. Additional methadone may "prime" cravings for heroin in metha done substitution patients.