Effect of CannEpil^® on simulated driving performance and co-monitoring of ocular activity: A randomised controlled trial

Abstract

Background: Medicinal cannabis products containing Δ9-tetrahydrocannabinol (THC) are increasingly accessible. Yet, policy guidelines regarding fitness to drive are lacking, and cannabinoid-specific indexations of impairment are underdeveloped. Aims: To determine the impact of a standardised 1 mL sublingual dose of CannEpil®, a medicinal cannabis oil containing 100 mg cannabidiol (CBD) and 5 mg THC on simulated driving performance, relative to placebo and whether variations in vehicle control can be indexed by ocular activity. Methods: A double-blind, within-subjects, randomised, placebo-controlled, crossover trial assessed 31 healthy fully licensed drivers (15 male, 16 female) aged between 21 and 58 years ( M = 38.0, SD = 10.78). Standard deviation of lateral position (SDLP), standard deviation of speed (SDS) and steering variability were assessed over time and as a function of treatment during a 40 min simulated drive, with oculomotor parameters assessed simultaneously. Oral fluid and plasma were collected at 30 min and 2.5 h. Results: CannEpil did not significantly alter SDLP across the full drive, although increased SDLP was observed between 20 and 30 min ( p < 0.05). CannEpil increased SDS across the full drive ( p < 0.05), with variance greatest at 20–30 min ( p < 0.001). CannEpil increased fixation duration ( p < 0.05), blink rate (trend p = 0.051) and decreased blink duration ( p < 0.001) during driving. No significant correlations were observed between biological matrices and performance outcomes. Conclusions: CannEpil impairs select aspects of vehicle control (speed and weaving) over time. Alterations to ocular behaviour suggest that eye tracking may assist in determining cannabis-related driver impairment or intoxication. Australian and New Zealand Clinician Trials Registry, https://anzctr.org.au(ACTRN12619000932167) .

A systematic review of oculomotor deficits associated with acute and chronic cannabis use

“…Acute THC administration did not impact blink duration, blink frequency, or eyelid opening in a pilot study 39 but did reduce blink duration in a more rigorously controlled experimental study 21 . Among individuals suspected of DUI, the presence of THC was associated with greater incidence of eyelid tremors compared with nondrug cases 7,8,40 .…”

“…Two articles 17,26 used an identical sample for their reports and are counted once in the demographic data. In experimental and observational cross‐sectional studies, ages ranged from 18 to 65 years, with two studies reporting an average age of ≥ 30 21,27 . In a single epidemiological study, ages ranged from 15 to 59 years 7 .…”

“…Throughout included experimental studies, THC was predominantly administered via inhalation methods, comprising of THC only cigarettes, 28,31,33,34,36,38,39 or THC in a vaporised form 29,30,32 . Two experimental studies administered THC via an oral solution 15,21 …”

“…Another three studies utilised consecutive doses of THC ranging from 12 mg THC 29,30 to 20 mg THC 32 within a single study session. A single experimental study administered a combined cannabinoid treatment of 5 mg THC and 100 mg cannabidiol 21 . THC dosages for several studies are unknown due to the inclusion of populations who were ongoing cannabis users 17,26,27,35,37 or were found to test positive for THC at the roadside 7,8,40 and, by design, were not experimentally administered quantifiable THC or cannabis dosages during study sessions.…”

“…(1) had no full-text available, (2) were nonhuman studies, (3) involved primarily nonadult populations, (4) involved administration or use of synthetic cannabinoids or phytocannabinoids only, (5) were an observational study with only self-reported cannabis use as a confirmatory measure or (6) measured changes in eye movement associated with REM during sleep, schizophrenia or cannabis-induced psychosis. 21 The full search criteria for this and resultant publications per database are available upon request.…”