Preliminary study of the interactive effects of THC and ethanol on self-reported ability and simulated driving, subjective effects, and cardiovascular responses

• Published in: Psychopharmacology Vol. 240; no. 6; pp. 1235 - 1246
• Main Authors: Schnakenberg Martin, Ashley M., Flynn, L. Taylor, Sefik, Esra, Luddy, Christina, Cortes-Briones, Jose, Skosnik, Patrick D., Pittman, Brian, Ranganathan, Mohini, D’Souza, Deepak Cyril
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2023; Springer; Springer Nature B.V
• Subjects: Alcohol; Alcoholism; Automobile Driving; Biomedical and Life Sciences; Biomedicine; Cannabis; Cardiovascular system; Care and treatment; Complications and side effects; Double-Blind Method; Dronabinol; Ethanol; Hallucinogens - pharmacology; Heart rate; Humans; Intoxication; Morbidity; Neurosciences; Original Investigation; Patient outcomes; Pharmacology/Toxicology; Placebos; Psychiatry; Psychomotor Performance; Self Report; Tetrahydrocannabinol; THC; United States; Heart rate; Cannabis; Cannabinoids; Ethanol; Subjective effects; Dronabinol; Driving; Alcohol; Intoxication; Tetrahydrocannabinol; THC
• ISSN: 0033-3158; 1432-2072; 1432-2072
• DOI: 10.1007/s00213-023-06356-0

Rationale Drug- and alcohol-related motor vehicle accidents are a leading cause of morbidity and mortality worldwide. Compared to alcohol, less is known about the effects of cannabis on driving and even less about their combined effects. Objective To characterize the combined and separate effects of ethanol and tetrahydrocannabinol (THC) on perceived ability to drive, subjective effects, and simulated driving. Methods In a within-subject (crossover), randomized, placebo-controlled, double-blind, 2 × 2 design, the effects of oral THC (10 mg [dronabinol] or placebo) and low-dose intravenous ethanol (clamped at BAC 0.04% or placebo) on perceived ability to drive, simulated driving (standard deviation of lateral position [SDLP]), subjective effects (e.g., “high”), and physiological effects (e.g., heart rate) were studied in healthy humans ( n  = 18). Results Subjects reported reductions in perceived ability to drive (THC < ethanol < combination) which persisted for ~ 6 h (placebo = ethanol, THC < combination). Ethanol and THC produced synergistic effects on heart rate, significant differences compared to either drug alone on perceived ability to drive and feeling states of intoxication (e.g., high), as well increases in SDLP compared to placebo. Conclusions Perceived ability to drive is reduced under the influence of THC against the backdrop of blood alcohol levels that are below the legal limit. People should be aware that the effects of oral THC on driving may persist for up to six hours from administration. Findings are relevant to the increasingly common practice of combining alcohol and cannabinoids and the effects on driving.