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

T. Kuitunen* **, T. Seppälä*, M.J. Mattila**, J. Pikkarainen*

* Department of Alcohol, Drugs and Traffic, National Public Health Institute, Laboratory of Pharmacology and Toxicology, Mannerheimintie 166, SF-00300 Helsinki, Finland

** Department of Pharmacology and Toxicology, University of Helsinki, Helsinki, Finland

ABSTRACT

The Finnish clinical test for drunkenness is a medicolegal test developed to detect alcohol-induced 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.

INTRODUCTION

The Finnish clinical test for drunkenness (CTD) is a medicolegal test battery used to detect alcohol-induced impairment of driving fitness in drunken drivers (Alha 1951). This test comprises motor, vestibular, mental, and behavioral subtests. Impairment of psychomotor performance measured with the CTD has been shown to correlate with blood alcohol concentrations (BACs) in statistical analyses (Penttilä et al. 1972, 1974) that have justified the medicolegal use of the CTD as the basis for court decisions in cases of drunken drivers.

At present, the CTD is carried out in Finland only in cases where drugs other than alcohol are suspected as contributing to impaired driving. The ability of the CTD to detect drug-induced impairments of performance has not previously been investigated systematically. The present study was conducted to investigate the applicability of the CTD to detect the effects of drugs acting on the central nervous system (CNS).

MATERIAL AND METHODS

The ability of the CTD to reveal the effects of single doses of ethanol alcohol (0.8-1.0 g/kg), benzodiazepines (BZDs, diazepam 15 mg, triazolam 0.25 mg, lorazepam 2 mg), zopiclone 7.5 mg, sedative antidepressant drugs (amitriptyline 50 mg, mirtazepine 15 mg), carbamazepine 600 mg, and those of ebastine 20 mg once daily for a week, on psychomotor performance, were compared with that of selected psychomotor laboratory tests, in four double-blind, crossover and placebo-controlled studies with a total of 60 healthy volunteers. Psychomotor laboratory tests included tracking, divided attention, digit symbol substitution, symbol copying, "global" psychomotor laboratory performance, critical flicker fusion threshold, Maddox wing, body sway and subjective assessments with visual analogue scales (VAS).

The relationships between BACs and blood BZD concentrations (after acute and chronic use), and psychomotor performance on the CTD 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. These data include the results of the CTD performed by doctors at municipal health centers and the BACs and blood drug concentrations analyzed, at the request of judicial authorities, by the National Public Health Institute.

RESULTS

The effects of drugs, alcohol, and drug-drug combinations on psychomotor laboratory tests and on the CTD performance in cross-over studies are shown in Tables 1-2. The field data revealed an association between mean blood BZD levels and the impairment of performance on all of the subtests of the CTD. The acute use of diazepam, characterized by a blood diazepam/nordiazepam ratio 3:1 or higher, was correlated with concentration-dependent impairment of motor and behavioral performance on the CTD (Kuitunen 1994).

Table 1
Effects of Alcohol and Drugs on Psychomotor Laboratory Tests

RT=reaction time; TESl=tracking error severity index; DSS=digit symbol substitution; SC symbol copying; CFF=critical flicker fusion; MW=Maddox wing. / separates data from two trials

* capsule ** sublingual tablet

- = no change, + = p<0.05, ++ = p<0.01 vs. placebo (three-way ANOVA+Duncan's multiple comparison)

Table 2
Effects of Alcohol and Drugs on the Subtests of the Clinical Test for Drunkenness in Healthy Volunteers

*capsule

**sublingual tablet

- = no change, + = p<0.05, ++ = p<0.01, +++ = p<0.001 vs. placebo (Wilcoxon matchedpairs test, Wilcoxon signed ranks test, Binomial test)

DISCUSSION

There are three ways to define illegal behavior as regards the use of drugs by drivers. The first is based on observation of the driver's clinical state, behavior, and other circumstantial evidence. The second is based on the identification of drugs in the biological fluids of the driver, and the third is the sum of these (Ferrara 1987).

The idea of formal penalty for drivers who are under the influence of drugs and/or alcohol is found in the laws of most countries. However, all countries having such laws admit the difficulty of applying them in the absence of a satisfactory tests to assess driving impairment (Irving 1988). It is of forensic importance that the tests used for law enforcement purposes are not so sensitive that innocent drivers would be prosecuted. However, the tests should have appropriate sensitivity to detect adequate numbers of drunken and drugged drivers from the road. According to Finnish law, a driver under the influence of drugs is liable to prosecution if the presence of significant amount of drug(s) in the driver's blood can be confirmed, impairment of performance has been demonstrated on the CTD, and the causative role of drugs is regarded as possible.

The experimental data showed that the CTD reveals the effects of drug-drug combinations but is less sensitive to the effects of single drugs. Lorazepam was an exception and caused the greatest impairments on motor and vestibular subtests, thus resembling alcohol. This agrees with Volkerts et al. (1987) who found that lorazepam 1 mg thrice within 8 hours impaired real driving on the road as much as, or even more than ethanol (0.15% in blood) did. On the other hand, psychomotor laboratory tests were sensitive in revealing the drug-induced impairment of performance.

Although the doses of alcohol were relatively low in the present laboratory studies, and the test populations were small, alcohol caused significant psychomotor impairment on the CTD, confirming that the test worked properly. Test situations in psychomotor laboratory settings differ from those in forensic practice where drivers suspected of breaking the laws are examined. The suspected offenders' degree of cooperation and motivation contributes substantially to medicolegal test results. Furthermore, interpretation of forensic tests is based on single administration of the tests, without establishing the subjects' baseline performance.

As to the epidemiological studies, alcohol led to results that agree with the previous data on the sensitivity of the CTD in revealing alcohol-induced impairments in performance (Penttilä et al. 1974). The CTD revealed the impairing effects of BZDs among drivers in real traffic. The acute use of diazepam was associated with concentration-dependent impairment of motor and behavioral performance. The tolerance developed to the effects of diazepam among chronic users may explain the paucity of significant concentration-effect relationships among chronic users. The concentration-response relationship between blood concentrations of different BZD derivatives and psychomotor performance on the CTD might be due to acute effects of BZDs.

CONCLUSIONS

Psychomotor laboratory tests were sensitive to the effects of drugs and drug-drug combinations acting on the CNS.

The CTD was sensitive to the effects of alcohol.

Single drugs alone had only minor effects on the CTD. Lorazepam was an exception, being the most potent BZD with the doses used.

Effects of drug-drug and drug-alcohol combinations were revealed by the CTD.

Blood BZD concentrations were associated with the impaired performance on the CTD in drivers suspected of driving under the influence of BZDs.

Blood diazepam concentration might be used as the basis for judicial decisions in acute cases having a blood diazepam/nordiazepam ratio of 3:1 or higher.

Validation of performance tests for medicolegal use is a challenge for future research.

REFERENCES

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Ferrara SD. Br J Addiction 82:871-883, 1987.

Irving A. Int Clin Psychopharmacol 3 (Suppl. 1): 13-21,1988.

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Penttilä A, Tenhu M, Kataja M. Blutalkohol 9:260-270, 1972.

Penttilä A, Tenhu M, Kataja M. Reports from Liikenneturva, Central Organization for Traffic Safety in Finland. 1974, 15, 1-78.

Volkerts ER, Brookhuis KA, O'Hanlon JF. Alcohol, Drugs and Traffic Safety - T86, pp. 217-222.