Evaluation of the reinforcing and subjective effects of heroin in combination with dextromethorphan and quinidine.

OBJECTIVE Studies have suggested that the N-methyl-D-aspartate antagonist dextromethorphan may be useful in the treatment of opioid dependence. DESIGN This double-blinded, placebo-controlled inpatient study evaluated the effects of 0, 30, and 60 mg of dextromethorphan and quinidine (DMQ) on the reinforcing and subjective effects of heroin in recently detoxified heroin abusers. PARTICIPANTS Nine heroin-dependent participants were admitted and then detoxified from heroin over the course of several days. INTERVENTIONS Participants were subsequently stabilized on 0, 30, or 60 mg of DMQ. Each dose of DMQ was administered for two consecutive weeks, and the effects of heroin (0, 12.5, and 50 mg) were studied under each DMQ maintenance dose condition. DMQ and heroin dose were administered in random order both within and between participants. RESULTS Planned comparisons revealed statistically significant increases in progressive ratio breakpoint values and positive subjective ratings as a function of heroin dose. There were no consistent changes in any of the responses as a function of DMQ maintenance dose, other than a modest reduction in craving. CONCLUSIONS In summary, results from this study suggest that maintenance on dextromethorphan in combination with quinidine has a limited role in the treatment of opioid dependence.