Can a simple clinical test detect impairment of zopiclone and alcohol? – A randomized controlled trial

• A simplified clinical test was less sensitive than psychomotor tests in detecting impairment.
• A positive clinical test result can still be useful for roadside impairment detection.
• It can indicate impairing blood levels of ethanol and zopiclone with high specificity.

PurposeThe risk of traffic accident involvement is increased among patients prescribed the z-hypnotic drug zopiclone. Clinical test observations able to indicate drug impairment are therefore essential. This study compared the findings of a simplified clinical test of impairment (SCTI) with those of a battery of computerized psychomotor tests of impairment (CPTI).Methods16 healthy young male volunteers attended a research unit on four different study days, receiving in randomized order either placebo, zopiclone 5 mg, zopiclone 10 mg, or alcohol 50 g. The SCTI was performed twice and the CPTI was performed three times on each study day, with blood samples being collected for drug analysis.ResultsThe SCTI (and the CPTI) was able to demonstrate impairment at 1.5 h, but no major impairment was found at 7 h with the SCTI, after intake of both zopiclone and ethanol. The CPTI detected a significantly higher proportion of impaired observations than the SCTI, both for zopiclone and for ethanol, at all concentration levels. The sensitivity of the clinical tests in detecting blood drug concentrations often associated with impairment, due to zopiclone (above 23 ng/ml) and alcohol (above 0.5 g/l), was low, revealing 27 per cent and 18 per cent, respectively. The specificity, however, was higher, both for zopiclone (88 per cent) and for alcohol (96 per cent).DiscussionThe SCTI may be a useful tool, especially during roadside investigation, when the police are in doubt as to whether the apprehended driver is impaired or not. A subject, who has consumed zopiclone or alcohol, tested with the SCTI, with one or more subtests diverging from a habitual result, is likely to have a blood zopiclone concentration above 23 ng/ml or a BAC above 0.5 g/l. A negative result, however, is less helpful.