Effects of ethanol on psychomotor performance under steady-state conditions.

Ethanol was administered to eight male volunteers using an oral loading dose followed by repeated small oral doses to achieve approximate steady-state drug concentrations in a double-blind placebo controlled cross-over design. Ethanol or placebo were administered over a 5-h period in two sessions at least 7 days apart. The effects of ethanol were assessed using a short battery of psychomotor tests and visual analogue scales which was administered repeatedly during the steady-state period, and a long battery administered once before and once during the steady-state period. The concentrations of ethanol in plasma and breath were determined at 20-min intervals. Mean plasma concentrations of 94 mg/100 ml were obtained. Ethanol produced a clear impairment to psychomotor performance, with a 41% increase in body sway, a 61% increase in errors on a maze task, a 6.5% reduction in digit-symbol substitution and an 8% slowing in tapping. Subjective feelings of drunkenness and sedation were noted. No measure showed evidence for acute tolerance, as assessed by comparison of the slopes fitted to the performance measures in the short battery.