Interaction between Marihuana and Ethanol: Effects on Psychomotor Performance

Abstract

This is a report of the results of a placebo-controlled study in which the effects of the interaction between ethanol and marihuana on drug plasma concentrations, subjective ratings of intoxication, heart rate acceleration, and psychomotor performance were investigated. Six healthy, male, paid volunteers, moderate users of ethanol and marihuana, participated in the study. Ethanol (0.42 g/kg, 0.85 g/kg, or placebo) was administered over a 30-min interval. Fifteen minutes later the subjects smoked, in their customary manner, NIDA cigarettes containing 2.4% or 0.0004% (placebo) delta-9-tetrahydrocannabinol (THC). Each subject was tested in a single-blind, latin-square crossover design with the following six conditions: placebo ethanol/placebo marihuana; low dose ethanol/placebo marihuana; high dose ethanol/placebo marihuana; placebo ethanol/marihuana; low dose ethanol/marihuana; and high dose ethanol/marihuana. The variables measured in the study were: (a) subjective rating of ethanol and/or marihuana intoxication; (b) heart rate; (c) accuracy and latency of response in the Simulator Evaluation of Drug Impairment (SEDI) task; (d) blood ethanol concentration by gas chromatography; and (e) plasma concentration of THC by radioimmunoassay. The results indicate that the decrements due to ethanol in performance of skills necessary to drive an automobile were significantly enhanced by marihuana in an additive and perhaps synergistic manner. The administration of ethanol prior to marihuana smoking did not produce significant effects on the subjective rating of "high," heart rate acceleration, or THC plasma concentration.

Controlled Cannabis Vaporizer Administration: Blood and Plasma Cannabinoids with and without Alcohol

“…Alcohol before smoking did not significantly affect THC C max (28 -29 ). Similar results were reported in another study, which also found no significant differences in plasma THC C max or AUC after ingesting 420 and 850 mg/kg alcohol vs placebo alcohol (cannabis smoked 0.25 h post- alcohol) (30 ). Plasma THC increased nonsignificantly but dose-dependently with increasing alcohol.…”

Alcohol Badly Affects Eye Movements Linked to Steering, Providing for Automatic in-Car Detection of Drink Driving

“…Many aspects of driving performance are impaired by even modest doses of alcohol. These include lane keeping, manifest as steering instability and crossing the center line (Ramaekers et al, 2000;Weiler et al, 2000); complex psychomotor tasks such as brake reaction time to an unexpected vehicle blocking the lane, and choice reaction time (Perez-Reyes et al, 1988;Liguori et al, 1999;Weiler et al, 2000); ability to divide attention appropriately between competing tasks and in general information processing (Moskowitz et al, 1985;Ogden and Moskowitz, 2004).…”

2007 National Roadside Survey of Alcohol and Drug Use by Drivers: Drug Results

“…Jones et al (2003) adds that Smiley's finding is relevant to the multitasking essence of driving, in particular by making marijuana-impaired drivers perhaps less able to handle unexpected events. Interestingly, there is also evidence showing that, unlike alcohol, marijuana enhances rather than mitigates the individual's perception of impairment (Lamers & Ramaekers, 1999;Robbe & O'Hanlon, 1993;Perez-Reyes, Hicks, Bumberry, Jeffcoat, & Cook, 1988). Robbe and O'Hanlon (1993) reported that in laboratory conditions, drivers under the influence of marijuana were aware of their impairment, which led them to decrease speed, avoid passing other vehicles, and reduce other risk-taking behaviors.…”