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Drug Alcohol Depend. 2015 Sep 1;154:25-37. doi: 10.1016/j.drugalcdep.2015.06.015. Epub 2015 Jun 23.

Cannabis effects on driving lateral control with and without alcohol.

Author information

1
Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, NIH, 251 Bayview Boulevard Ste 200 Rm 05A721, Baltimore, MD, USA; Program in Toxicology, University of Maryland Baltimore, 660 West Redwood Street, Baltimore, MD, USA.
2
National Advanced Driving Simulator, University of Iowa, 2401 Oakdale Boulevard, Iowa City, IA, USA.
3
College of Pharmacy, University of Iowa, Iowa City, IA, USA.
4
Variable Solutions, USA.
5
Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, NIH, 251 Bayview Boulevard Ste 200 Rm 05A721, Baltimore, MD, USA; Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA.
6
Carver College of Medicine, University of Iowa, Iowa City, IA, USA.
7
Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, NIH, 251 Bayview Boulevard Ste 200 Rm 05A721, Baltimore, MD, USA. Electronic address: mhuestis@intra.nida.nih.gov.

Abstract

BACKGROUND:

Effects of cannabis, the most commonly encountered non-alcohol drug in driving under the influence cases, are heavily debated. We aim to determine how blood Δ(9)-tetrahydrocannabinol (THC) concentrations relate to driving impairment, with and without alcohol.

METHODS:

Current occasional (≥1×/last 3 months, ≤3days/week) cannabis smokers drank placebo or low-dose alcohol, and inhaled 500mg placebo, low (2.9%)-THC, or high (6.7%)-THC vaporized cannabis over 10min ad libitum in separate sessions (within-subject design, 6 conditions). Participants drove (National Advanced Driving Simulator, University of Iowa) simulated drives (∼0.8h duration). Blood, oral fluid (OF), and breath alcohol samples were collected before (0.17h, 0.42h) and after (1.4h, 2.3h) driving that occurred 0.5-1.3h after inhalation. We evaluated standard deviations of lateral position (lane weave, SDLP) and steering angle, lane departures/min, and maximum lateral acceleration.

RESULTS:

In N=18 completers (13 men, ages 21-37years), cannabis and alcohol increased SDLP. Blood THC concentrations of 8.2 and 13.1μg/L during driving increased SDLP similar to 0.05 and 0.08g/210L breath alcohol concentrations, the most common legal alcohol limits. Cannabis-alcohol SDLP effects were additive rather than synergistic, with 5μg/L THC+0.05g/210L alcohol showing similar SDLP to 0.08g/210L alcohol alone. Only alcohol increased lateral acceleration and the less-sensitive lane departures/min parameters. OF effectively documented cannabis exposure, although with greater THC concentration variability than paired blood samples.

CONCLUSIONS:

SDLP was a sensitive cannabis-related lateral control impairment measure. During drive blood THC ≥8.2μg/L increased SDLP similar to notably-impairing alcohol concentrations. Despite OF's screening value, OF variability poses challenges in concentration-based effects interpretation.

KEYWORDS:

Alcohol; Cannabis; Driving; Lateral control; Oral fluid; THC

PMID:
26144593
PMCID:
PMC4536116
DOI:
10.1016/j.drugalcdep.2015.06.015
[Indexed for MEDLINE]
Free PMC Article

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