Drug-seeking behavior during methadone maintenance

Six subjects were given the opportunity to work for saline placebo and hydromorphone (4 mg i.v.) several times weekly before and during a period of maintenance on methadone (100 mg p.o. daily). Measures of pupillary change and reports of "liking" in response to hydromorphone dropped to saline control levels when the daily dose of methadone was approximately 60 mg. Half of the subjects continued to work intermittently for hydromorphone for four weeks while they were receiving 100 mg of methadone daily. These data support the assumption that methadone maintenance reduces the reinforcement value of other opiates and behaviors associated with obtaining them.