Combined effects of acute, very-low-dose ethanol and delta(9)-tetrahydrocannabinol in healthy human volunteers.
BACKGROUND
Previous studies examining the combined effects of ethanol and cannabis, or its primary psychoactive ingredient, ∆⁹-tetrahydrocannabinol (THC), have provided mixed results. Data from an in vitro study suggests that combined, sub-threshold doses of these drugs may interact to produce synergistic effects. Very low doses of the two drugs in combination have not been tested in humans.


METHODS
This study assessed whether combinations of acute, very low doses of ethanol and THC produce synergistic effects on subjective, cognitive, and physiological measures. Healthy volunteers (n=11) received capsules containing placebo or THC (2.5 mg), and beverages containing placebo or ethanol (0.1 and 0.2 g/kg) alone, and in combination, across separate sessions, in a within-subjects, randomized, double-blind design. During each session, participants completed measures of working memory, psychomotor ability, and simple reaction time, and provided subjective mood and drug effect ratings. Cardiovascular measures were obtained at regular intervals.


RESULTS
As intended, when administered alone, these very low doses of ethanol and THC had only moderate effects on isolated measures. The combined effects of these drugs were not synergistic, and in some cases appeared to be less-than-additive.


CONCLUSIONS
Our data provide no evidence for synergistic effects of acute combinations of very-low-dose ethanol and THC on subjective or physiologic response, or on cognitive performance.
Department of Psychiatry and Behavioral Neuroscience, The University of Chicago, Chicago, IL 60637, USA.
Michael E
ME
Ballard
Harriet
H
de Wit
D000328:Adult; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D013759:Dronabinol / Q000008:administration & dosage / Q000494:pharmacology*; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D010919:Placebos; D012016:Reference Values
D010919:Placebos; D000431:Ethanol; D013759:Dronabinol