The barbiturates consist of a pyrimidine nucleus derived from the condensation of malonic acid and urea. Pharmacologically, barbituric acid per se does not have central nervous system (CNS) depressant action. The CNS action is produced only after the appropriate alkyl or aryl groups are substituted on the carbon 5,5′ positions. Accordingly, barbiturates used in therapy possess various substitutional groups at the carbon 55′ positions. The following requirements when substituted appear to be important for production of the pharmacological activity (cf Sharpless, 1970 ; Andrews et al., 1979 ).