EFFECTS OF AN ALTERNATIVE REINFORCER ON INTRAVENOUS HEROIN SELF-ADMINISTRATION BY HUMANS

Five heroin-dependent research volunteers, maintained on divided daily oral morphine doses, participated in an inpatient study designed to e valuate intravenous (i.v.) heroin self-administration when money ($10, $20 or $40) was concurrently available. Each morning participants rec eived a single injection of heroin (placebo, 6.25, 12.5, 25, or 50 mg/ 70 kg, i.v.) and each afternoon, they had the opportunity to self-admi nister all or part of the morning dose. Participants responded under a progressive-ratio schedule (50, 100, ..., 2800) during a 10-trial sel f-administration task. During each trial, participants could respond f or 1/10th of the sampled heroin dose or 1/10th of a single money value . The progressive-ratio value increased independently for each option. The total amount of heroin and/or money chosen during the self-admini stration task was administered at the end of the task. Heroin dose-dep endently increased ratings of 'good drug effect' and 'high', impaired task performance and decreased pupil diameter and blood oxygen saturat ion. Heroin also dose-dependently increased progressive-ratio break po int values, which varied as a function of the alternative money amount . Consistent with previous studies, the present results demonstrate th at alternative reinforcers, depending on magnitude, are effective in r educing heroin use in opioid-dependent individuals. (C) 1998 Elsevier Science B.V.