A study was undertaken to examine the effects of methadone, as used in the methadone maintenance program, on human performance skills which are related to those required to drive a motor vehicle with safety. The tests used were chosen for their relevance to driving as well as for the distinctive properties of the opioids. The interaction between methadone and two other drugs commonly used by clients on a methadone program were also examined. These were (i) alcohol, to produce a mean blood alcohol concentration at peak of 0.064 g per 100 ml blood and (ii) a therapeutic dose of diazepam (15 mg). The test battery proved to be sensitive to the effects of alcohol and diazepam at the doses used. There was no evidence for an effect of the acute dose of methadone on any of the experimental groups of clients on the methadone program. These results suggest that these clients should not be considered as impaired in their ability to perform complex tasks such as driving a motor vehicle. Both alcohol and diazepam produced a significant decrement in the performance on the test battery by the control groups and the stabilized methadone clients. There was no difference in the intensity of this effect between the groups. There was no evidence for an interaction between methadone and either alcohol or diazepam in the group of methadone clients stabilized on the program. (A)
Abstract