Actions and Interactions of Diazepam and Alcohol on Psychomotor Skills in Young and Middle‐aged Subjects

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Abstract
Healthy pretrained men participated in 3 separate controlled double-blind and cross-over trials. There were 10 students in trial I, 11 army officials or policemen aged 38-59 yr in trial II, and 11 students in trial III. After single oral doses of diazepam 10 mg (D), placebo,alcohol 0.5 g/kg (A) or D + A, given at 1-wk intervals in balanced order, the psychomotor skills (choice reaction, tracking, attention, flicker fusion) were repetitively measured up to 2.5 h. Serum D concentrations were measured by gas chromatography. D alone impaired flicker fusion in trials I and II and also reactive and coordinative skills in trial III. A alone slightly impaired skills and failed to potentiate D effects. Increasing age rendered the performance worse but this was due to increased base-line errors rather than to enhanced responses to D. Serum D concentrations rose in the presence of A suggesting an inhibition of D demethylation by alcohol. Both total and free concentrations of D were similar in both age groups. Despite unaltered sensitivity to D, middle-aged subjects may have a lowered margin of safety when driving or using machinery under D treatment.