The cannabinoids (THC, 215 μ/kg; CBD, 320 μg/kg; CBN, 320 μg/kg) and ethanol (0.54 g/kg) were administered orally to human volunteers alone and in all possible combinations and performance decrements were assessed on a battery of tests (standing steadiness, simple and complex reaction times, pursuit rotor and Vienna Determination Apparatus) over a 280 min period. Blood ethanol concentrations and pulse rates were measured, an assessment was made of conjunctival hyperaemia and the subjects were asked to estimate the nature and degree of their intoxication.
THC alone produced significant decrements on all the performance measures (general performance, standing steadiness, reaction speed and psychomotor performance) which were slow in onset, and were still evident at the end of the experiment. The increases in pulse rates and conjunctival hyperaemia as well as the subjects' assessment of their intoxication followed a similar time course. Ethanol also produced significant decrements in all but the psychomotor co-ordination factor which were rapid in onset with complete recovery by the end of the test period. There was no suggestion of systematic effects involving CBD or CBN, either alone or in combination with other drugs, and it was possible to describe the data in terms of a model which referred only to the effects of THC and ethanol.
The combined effects of THC and ethanol were greater than those of THC alone, both in the performance measures, where virtually no recovery occurred, and in the self-assessment of intoxication and could be described in terms of an additive model with no statistical evidence for interaction. Blood ethanol levels were unaffected by cannabinoid pretreatment.
There was no suggestion that the effects of THC or THC plus ethanol were further modified in any was by the inclusion of CBD and/or CBN in the cannabinoid pretreatment.
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Bird, K.D., Boleyn, T., Chesher, G.B. et al. Intercannabinoid and cannabinoid-ethanol interactions and their effects on human performance. Psychopharmacology 71, 181–188 (1980). https://doi.org/10.1007/BF00434409