Sigmodal (Rectidon) is a barbiturate derivative. It has sedative, hypnotic and anticonvulsant properties, and was used in surgical anaesthesia in the 1950s, and frequently appeared in drug mixtures in the 60s.[1] [2]
It was never widely used compared to better known barbiturates such as thiopental, and has now been replaced by newer drugs with a better safety profile.