Mental and Psychomotor Effects of Diazepam and Ethanol

The performance of eight healthy young males was tested by means of 8 psychological and psychomotor tests 1 3 / 4 and 4 1 / 2 hrs after the administration of either ethanol, diazepam 10 or 20 mg, or placebo. The mean plasma concentrations of diazepam were estimated to be 230 (10 mg dose) and 495 ng/ml (20 mg) respectively after 1 3 / 4 hr and 145 (10 mg), and 310 ng/ml (20 mg) after 4 1 / 2 hrs; ethanol was estimated to be 0.091% after 1 3 / 4 hr and 0.049% after 4 1 / 2 hrs. Diazepam produced stronger subjective sensations of relaxation and reduced concentration than ethanol, whereas the test subjects experienced a similar depressing effect on motivation and effectivity after ethanol and after the largest dose of diazepam (20 mg). Both diazepam and ethanol reduced the scores in the following tests: Memorizing, Sorting (of coloured tablets), Complex Coordination and Critical Flicker Fusion Frequency. The scores in Letter‐Cancellation and Mirror Tracing tests were also reduced by both drugs, but in different ways; ethanol made the test subjects attempt more but increased their number of errors, while diazepam on the other hand slowed the subjects, so that they made fewer mistakes, but attempted less. Diazepam (20 mg) also reduced their time evaluation ability, while ethanol did not affect it significantly. Judged by clinical examination diazepam had a less marked effect on proprioception, speech and balance than ethanol. The effect of diazepam on the Flicker Fusion and Mirror Tracing tests could still be recognized 4 1 / 2 hr after administration of the drug.