Dexamphetamine and alcohol effects in simulated driving and cognitive task performance

This study assessed the effects of dexamphetamine with and without alcohol on simulated driving and cognitive tasks. 18 subjects participated in all 4 conditions: 10 mg dexamphetamine and 0.8g/kg alcohol, 10 mg dexamphetamine only, 0.8g/kg alcohol only, and a placebo control condition. A driving simulator was used to assess driving skills and risk taking on different road types. Cognitive performance was assessed using vigilance and divided attention tasks and subjects completed different rating scales. The main effects found were those of alcohol. This related to a larger standard deviation of lateral position, shorter accepted gap time and distance, higher average and maximum driving speeds and more violations of speed limits. A higher percentage of subjects in the dexamphetamine + alcohol condition did not stop for the red traffic lights, or collided with a vehicle. Performance of vigilance and divided attention tasks was impaired in the alcohol condition and impaired to a lesser degree in the dexamphetamine + alcohol condition. The conclusions of this study are that the main effect of impaired driving was found in the effect of 0.8 g/kg alcohol dose at the control level and the maneuvering level. The amphetamine dose did not potentiate risk taking behaviour, but also did not overcome the negative effects of alcohol. The findings of the present study justify the conclusion that drivers using 0.8 g/kg alcohol, or the combination of dexamphetamine with alcohol, pose a considerable traffic safety risk.