MDMA and alcohol effects, combined and alone, on objective and subjective measures of actual driving performance and psychomotor function

Rationale The party drug ecstasy is frequently used in combination with other drugs like marihuana and alcohol. In addition, a substantial proportion of the MDMA users has claimed to drive a car when under the influence of MDMA and/or other drugs. Objective To assess the effects of MDMA and alcohol, combined and alone, on actual driving performance and laboratory tasks related to driving. Methods Eighteen healthy subjects participated in a double-blind, placebo-controlled, six-way cross-over study. Treatments consisted of MDMA 0, 75, and 100 mg with and without alcohol, aiming at 0.06 mg/ml BAC. Laboratory tests (critical tracking task, object movement estimation task) were conducted between 1.5 and 2 h postdrug (0.5 and 1 h postalcohol). Actual driving tests (road tracking test, car-following test) were conducted between 3 and 5 h postdrug (2 and 4 h postalcohol). Subjects completed the addiction research center inventory (ARCI) and rated their driving quality and mental effort during driving. Results Alcohol alone impaired critical tracking performance, as well as a number of actual driving performance parameters [i.e., standard deviation of lateral position (SDLP), brake reaction time, and coherence]. MDMA alone reduced SDLP and standard deviation of speed. MDMA significantly moderated alcohol induced impairment of road tracking performance but did not affect alcohol impairments of car-following and laboratory task performance. Subjective data seemed to support objective data. Conclusions MDMA moderated the impairing effects of a low dose of alcohol on road tracking performance but it could not overcome alcohol-induced impairment on other aspects of driving behavior or driving related performance.