Short‐term effects of oral methadone in methadone maintenance subjects

In two experiments the physiologic and subjective status of methadone maintenance patients was assessed during the presumed peak (0 to 6 hr postmethadone) and during the presumed nadir of the daily methadone effect (18 to 30 hr postmethadone). In the first experiment physiologic and subjective responses were measured in seven ambulatory subjects at 2, 4, and 6 hr after a regular daily dose of methadone or placebo. In the second, physiologic measures were continuously monitored for 4 hr in six inactive seated subjects. In both studies, pupil diameter decreased after moderate to high methadone doses (35 to 80 mg). In the second experiment, heart rate fell and skin temperature rose significantly after methadone. Responses to the morphine‐benzedrine group scale of the Addiction Research Center Inventory were elevated after methadone for most subjects in both studies, although there were individual differences in the magnitude and time course of this effect. Finally, low methadone maintenance doses of 10 and 20 mg/day had little or no effect on physiologic or subjective responses in two subjects. These studies showed that short‐term effects of oral methadone can be readily detected during a 24‐hr dosing regimen. The changes in function after the regular maintenance dose may result both from short‐term opiate effects and relief of mild withdrawal. Clinical Pharmacology and Therapeutics (1982) 31 , 753–761; doi: 10.1038/clpt.1982.106