CORRELATION BETWEEN BLOOD DIAZEPAM CONCENTRATIONS AND PERFORMANCE ON THE CLINICAL TEST FOR DRUNKENNESS IN ACUTE AND CHRONIC DIAZEPAM USERS

The clinical test for drunkenness (CTD) is a medico-legal test battery comprising 13 simple motor, vestibular, mental and behavioral subtests. In Finland it has been used to examine the driving fitness of drunken and drugged drivers. Between 1977 and 1992, blood and urine samples from 10,976 drivers suspected of driving under the influence of drugs or drugs and alcohol were analyzed for drugs at the National Public Health Institute in Finland. During this period 130 drivers were positive for diazepam only and were used as subjects to analyze the sensitivity of the CTD to diazepam. Acute and chronic use of diazepam was differentiated on the basis of the ratio of diazepam to nordiazepam in the blood. A ratio of 3:1 or higher was regarded as indicating acute diazepam intake. Acute diazepam users (n = 31) were significantly younger than chronic users (n = 99). Their overall state of inebriation and impairment of performance on walking with eyes open and closed and on pooled motor and behavioral tests correlated significantly with blood diazepam concentrations in acute users. Among acute diazepam users, blood diazepam concentrations were significantly higher in drivers showing impaired performance on walking with the eyes closed compared to drivers exhibiting normal performance. In chronic users, impairment of speech was the only parameter which correlated significantly with blood diazepam levels. The data suggest that the CTD is sensitive to acute benzodiazepine effects in a concentration dependent way, whereas prolonged administration of diazepam leads to a tolerance phenomenon that diminishes the usefulness of blood concentrations as the basis of judicial decision-making.