The effect of delta 9-tetrahydrocannabinol, cannabidiol, and cannabinol on the anaesthesia induced by various anaesthetic agents in mice.

delta 9-Tetrahydrocannabinol (2.5-80.0 mg/kg) significantly prolonged the anaesthesia induced by ketamine, pentobarbitone, thiopentone, propanidid, and Alfathesin in a dose-dependent manner. Cannabinol and cannabidiol (both 5.0-80.0 mg/kg) were essentially inactive, except that cannabidiol prolonged pentobarbitone-induced anaesthesia. The interaction of delta 9-tetrahydrocannabinol with the anaesthetic agents was postulated to be due to a centrally mediated action, whereas the effect of cannabidiol on pentobarbitone-induced anaesthesia probably depended on a metabolic interaction. The interaction between the cannabinoids in influencing anaesthesia induced by the above agents was examined, and the interactions were found to be complex.