SEDATIVE ACTIVITY OF CANNABIS IN RELATION TO ITS Δ‘‐trans‐TETRAHYDROCANNABINOL AND CANNABIDIOL CONTENT

Abstract

The oral sedative potencies of cannabis herb, crude ethanolic and petroleum‐ether fractions, were assayed against Δ′‐trans‐tetrahydrocannabinol (THC) administered orally to mice, by measuring spontaneous motor activity over 30 min periods, at selected times, up to 6 h. The THC contents of the extracts were determined chemically by gas‐liquid chromatography analysis and the B/C ratio (biological activity divided by chemical activity) calculated for each. The B/C values for cannabis herb, which contained THC but no CBD, was 4.47 and for ethanolic and petroleum‐ether extracts, 5.26 and 4.39, respectively. The sedative potency expressed as SDA50, the dose required to give 50% effect over 6 h, was 1.06 (0.98 to 1.15) mg/kg for THC; 4.72 (4.22 to 5.27) mg/kg for cannabidiol and 1.26 (1.22 to 1.80) mg/kg for chlorpromazine. An infusion of cannabis herb made with boiling water was shown to have sedative activity of very low potency. When the cannabinoids were completely extracted from a sample of herb with petroleum‐ether the aqueous and ethanolic extracts of the marc had some sedative activity; but the 70% ethanolic fraction had none. The sedative activity of THC, cannabis herb and a water soluble fraction is blocked by aspirin, a cyclo‐oxygenase inhibitor, and restored by prostaglandin E2 (PGE2). The sedative effect of chlorpromazine is not blocked by aspirin. 1981 British Pharmacological Society