Drug and ethanol effects on the clinical test for drunkenness: single doses of ethanol, hypnotic drugs and antidepressant drugs.

The clinical test for drunkenness has been used in Finland to detect alcohol-induced impairment of driving fitness. Since the data about the effects of psychotropic drugs on the clinical test for drunkenness are limited, this test was administered in two randomized double-blind cross-over trials with 12 subjects in each. The clinical tests were done at 2 hr and 5 hr after drug intake. For comparison, the representative laboratory tests used were digit symbol substitution, simulated driving (tracking+reaction time) and "global psychomotor performance". In Trial I, 15 mg of diazepam, 50 mg of amitriptyline and 15 mg of mirtazepine, each drug administered alone, had minor effects on the clinical tests. Compared to the placebo, mirtazepine, and diazepam, diazepam+mirtazepine impaired performance on the motor subtests at 2 hr. The tracking error percentage was increased by amitriptyline, diazepam+amitriptyline, and diazepam+mirtazepine up to 4.5 hr. In Trial II with 7.5 mg of zopiclone, 0.25 mg of triazolam and 0.8 g/kg of ethanol, ethanol alone and hypnotic-ethanol combinations impaired performance on the motor and vestibular subtests, whereas single drug intake had minor effects. Tracking was more sensitive to drugs than to ethanol. In conclusion, the clinical test for drunkenness detected impaired performance following single doses of ethanol or drug-ethanol combinations better than it detected impaired performance following moderate doses of drugs or drug-drug combinations, respectively.