A cannabidiol (CBD) analog that acts as a selective antagonist of abnormal CBD (Abn-CBD) at the non-CB1/CB2 endothelial receptor; does not bind to CB1 or CB2 receptors at concentrations up to 30 µM and inhibits the vasorelaxant effects of Abn-CBD in vitro and in whole animals; blocks the Abn-CBD-induced activation of the PtdIns 3-kinase/Akt pathway in human umbilical vein endothelial cells.