O-1918 is a synthetic compound related to cannabidiol, which is an antagonist at two former orphan receptors GPR18 and GPR55, that appear to be related to the cannabinoid receptors. O-1918 is used in the study of these receptors, which have been found to be targets for a number of endogenous and synthetic cannabinoid compounds, and are thought to be responsible for most of the non-CB<sub>1</sub>, non-CB<sub>2</sub> mediated effects that have become evident in the course of cannabinoid research.
Subsequent research by using electrophysiological approach has shown that O-1918 is a potent BKCa channel inhibitor.