Lysergic acid cyclobutylamide (LAcB or C<sub>4</sub>AL), also known as N-cyclobutyllysergamide (NCB-LA), is a semisynthetic lysergamide that is synthesized from naturally occurring ergot alkaloids found in Claviceps purpurea. It has oxytocic effects on the isolated rat uterus similarly to other lysergamides, shows antiserotonergic effects in the isolated rat intestine similarly to lysergic acid diethylamide (LSD), has mydriatic effects similarly to LSD when administered to mice, and produces other biological effects. Despite being more effective than LSD in various bioassays however, LAcB did not have psychedelic effects in humans. The drug was first described in the scientific literature by 1958.