To investigate individual traffic-relevant impairment related to measured blood zopiclone and ethanol concentrations. Also, we aimed to study possible development of acute tolerance.
A randomized controlled 4-way crossover double blinded trial. Study drugs were zopiclone 5 or 10 mg, 50 g ethanol or placebo.
Laboratory study with computerized tests: Connors Continuous Performance test, Choice reaction time, and Stockings of Cambridge. Altogether, the tests consisted of 15 test components, representing 3 levels of behavior (automotive, control, executive planning), relevant to traffic safety.
16 healthy male volunteers.
Each study day, 10 blood samples were collected from each volunteer. 15 psychomotor test components were registered at baseline and a further 3 times after intake. Impairment was defined as any individual deterioration in performance compared to individual baseline performance.
Blood drug concentrations up to 74 µg/l zopiclone and 0.100 % ethanol were measured. We found a clear positive concentration-effect relationship for zopiclone and ethanol for both automotive and control behaviors, and a modest relationship for executive planning behavior. Significant impairment started to be observed at concentrations above 16 µg/l zopiclone (automotive and control behavior) and above 0.026 % ethanol (automotive behavior). Acute tolerance was found for both drugs.
The hypnotic, zopiclone, can impair psychomotor performance at blood concentrations as low as 16ug/ml.
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