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.
Conclusion: 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.