Oral methadone self-administration: Effects of dose and alternative reinforcers

Abstract

The efficacy of oral methadone as a reinforcer was examined by offering methadone maintenance patients the chance to self-administer extra doses of methadone occasionally in addition to their regular dose. Seven maintenance patients required twice-weekly choices between methadone doses or money. Doses were 0, 1, 5, 10, 25 or 50 mg methadone; the alternative money option was 1 or 5 dollars. Extra methadone doses were reliably self-administered by maintenance patients, and percent of dose choices rose as the size of the dose offered increased. Extra methadone doses functioned as reinforcers in this situation. Across the entire dose range, more dose choices were selected when 1 dollar was offered than when 5 dollars were offered as an alternative. Methadone self-administration was influenced by the alternative reinforcers available for drug refusal. Neither reports of subjective withdrawal symptoms nor reduction of symptoms after extra methadone predicted methadone self-administration, but dose selections were more likely when urinalysis results indicated recent illicit opiate use. The reinforcing effects of oral methadone in methadone-tolerant patients may be an important factor in the popularity of this treatment among drug abusers and in the long-term treatment retention generally observed during methadone maintenance.