EFFECTS OF ETHANOL ON PSYCHOMOTOR PERFORMANCE UNDER STEADY-STATE CONDITIONS

Ethanol was administered to eight male volunteers using an oral loadin g dose followed by repeated small oral doses to achieve approximate st eady-state drug concentrations in a double-blind placebo controlled cr oss-over design. Ethanol or placebo were administered over a 5-h perio d in two sessions at least 7 days apart. The effects of ethanol were a ssessed using a short battery of psychomotor tests and visual analogue scales which was administered repeatedly during the steady-state peri od, and a long battery administered once before and once during the st eady-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 psycho motor 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 s edation were noted. No measure showed evidence for acute tolerance, as assessed by comparison of the slopes fitted to the performance measur es in the short battery.