The Finnish Clinical Test for Drunkenness in Evaluating the Effects of Drugs on Driving Fitness

The Finnish clinical test for drunkenness is a medicolegal test developed to detect alcoholinduced impairment of driving fitness. This test comprises motor, vestibular, mental and behavioral subtests. The ability of the clinical test for drunkenness to reveal drug-effects on performance was compared with that of selected psychomotor laboratory tests. Psychomotor laboratory tests included simulated driving, digit symbol substitution, divided attention, critical flicker fusion, Maddox wing, body sway, memory and learning, and ‘global’ psychomotor laboratory test performance and subjective assessments with visual analogue scales and questionnaires on side-effects. The effects of alcohol, benzodiazepines (diazepam, triazolam, lorazepam), zopicione, sedative antidepressant drugs (amitriptyline, mirtazepine), carbamazepine, and ebastine were studied in four double-blind, crossover and placebo-controlled studies with a total of 60 healthy volunteers. The relationships between blood alcohol concentrations and blood benzodiazepine concentrations, and psychomotor performance on the clinical test for drunkenness were studied in two field studies using medicolegal data files on a total of 387,770 Finnish drivers kept centrally by the National Public Health Institute. Psychomotor laboratory tests were sensitive in revealing the effects of drugs and drug-drug combinations. Alcohol clearly impaired performance on the clinical test for drunkenness in both crossover and field studies. Single drugs alone had only minor effects on the clinical test for drunkenness, but this test detected effects of drug-drug and drug-alcohol combinations. Blood benzodiazepine concentrations were associated with impaired performance on the clinical test for drunkenness. This may in part be due to acute use of benzodiazepines, as suggested by the correlation of blood diazepam concentrations with impaired performance on the clinical test for drunkenness after acute use of diazepam. It is concluded that the clinical test for drunkenness reveals the effects of alcohol, drug-drug, and drug-alcohol combinations better than those of single drugs alone which, in turn, are easily detected with psychomotor laboratory tests.