SPL Set ID: 4e2910f2-173d-4b5c-aad3-44f4ab40d8cb

The barbiturates are nonselective central nervous system (CNS) depressants that are primarily used as sedative-hypnotics. In subhypnotic doses, they are also used as anticonvulsants. The barbiturates and their sodium salts are subject to control under the Federal Controlled Substances Act. Phenobarbital is a barbituric acid derivative and occurs as white, odorless, small crystals or crystalline powder that is very slightly soluble in water; soluble in alcohol, in ether, and in solutions of fixed alkali hydroxides and carbonates; sparingly soluble in chloroform. Phenobarbital is 5-ethyl-5-phenylbarbituric acid. Phenobarbital is a substituted pyrimidine derivative in which the basic structure is barbituric acid, a substance that has no CNS activity. CNS activity is obtained by substituting alkyl, alkenyl, or aryl groups on the pyrimidine ring. It has the following structural formula: C 12 H 12 N 2 O 3 M.W. 232.24 Each phenobarbital tablet contains 16.2 mg (1/4 grain), 32.4 mg (1/2 grain), 64.8 mg (1 grain) or 97.2 mg (1 1/2 grain) of phenobarbital. In addition each tablet contains: colloidal silicon dioxide, lactose monohydrate, magnesium stearate, microcrystalline cellulose and sodium starch glycolate. Chemical Structure