Effect of CannEpil on Simulated Driving Performance and Co-monitoring of Ocular Activity: A Randomised Controlled Trial

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 ( = 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 ( < 0.05). CannEpil increased SDS across the full drive ( < 0.05), with variance greatest at 20-30 min ( < 0.001). CannEpil increased fixation duration ( < 0.05), blink rate (trend  = 0.051) and decreased blink duration ( < 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).