Marijuana And Actual Driving Performance

U.S. Department of Transportation,
National Highway Traffic Safety Administration
(DOT HS 808 078), Final Report, November 1993

LABORATORY STUDY

Methods

Twenty-four subjects, equally comprised of men and women, participated in this study. They were allowed to smoke part or all of the THC content in three cigarettes until achieving the desired psychological effect. The only requirement was to smoke for a period not exceeding 15 minutes. When subjects voluntarily stopped smoking, cigarettes were carefully extinguished and retained for subsequent gravimetric estimation of the amount of THC consumed.

Results

Six subjects consumed one cigarette, thirteen smoked two and four smoked three (data from one male subject were excluded from the results because no drug was found in his plasma after smoking). The average amount of THC consumed was 20.8 mg, after adjustment for body weight, 308 g/kg. It should be noted that these amounts of THC represent both the inhaled dose and the portion that was lost through pyrolysis and side- stream smoke during the smoking process. There were no significant differences between males and females, nor between frequent and infrequent users, with respect to the weight adjusted preferred dose. It was decided that the maximum dose for subsequent driving studies would be 300 g/kg.