Drug Policy Implications of Inhaled Cannabis: Driving Skills and Subjective Effects, Vaporized Cannabinoid Pharmacokinetics, and Interactions with Alcohol

Abstract

Increasing medical and recreational cannabis legalization and shifting public attitudes are accompanied by increased driving under the influence of cannabis (DUIC) cases and changing administration routes, including vaporization. Cannabis' driving effects are poorly understood, and cannabis driving per se laws heavily debated--especially when considering blood collection delays. Cannabis and alcohol are frequently encountered together in drugged driving cases, but interactive effects are not fully elucidated. Oral fluid (OF) is an advantageous alternative matrix for documenting cannabis exposure, with interest in correlating cannabis' effects with OF cannabinoid concentrations. This research aimed to 1) evaluate cannabis' effect on driving lateral control relative to blood delta9-tetrahydrocannabinol (THC) concentrations, with and without alcohol; 2) assess vaporized cannabis' subjective effects and pharmacokinetic disposition in blood, plasma, and OF, with and without alcohol. Current cannabis smokers drank placebo or low-dose alcohol and inhaled vaporized placebo, low (2.9%), or high (6.7%)-THC vaporized bulk cannabis (6 conditions, within-subject). Participants drove 45min simulated drives 0.5h post-dose. Subjective effects, blood and OF, and breath alcohol concentration (BrAC) were measured at baseline and up to 8.3h post-dose. Cannabis increased standard deviation of lateral position (SDLP, lane weaving) but not maximum lateral acceleration or lane departures/min. BrAC increased all three; cannabis-alcohol SDLP effects were additive rather than synergistic. Cannabinoids' time courses and subjective effects exhibited patterns similar to those after smoking, with THC maximum concentration (Cmax) occurring immediately post-dose and decreasing rapidly thereafter, then subsequent slower excretion. Approximately half of participants self-titrated doses to individual comfort levels via inhalation technique, resulting in similar THC Cmax after low and high doses. Blood THC concentrations 7-10ug/L during driving increased SDLP similarly to 0.05g/210L [impairing] BrAC; 20ug/L, more than 0.08g/210L [US illegal BrAC]. Because SDLP effects were additive, 5ug/L THC+0.05g/210L alcohol produced similar SDLP to 0.08g/210L. Blood THC during driving generally is much higher than at time of blood draw in authentic DUIC cases. OF cannabinoids documented intake, but THC concentration variability limited interpretation. Data demonstrate significant cannabis effects on driving, provide blood and OF concentrations after vaporized cannabis, and will benefit clinicians and policymakers by improving DUIC and clinical interpretation.