Phenobarbital [Phenobarbitone]

This chapter presents a trade name, classification, approved indications for psychological disorders, available dosage forms, storage, and compatibility, usual dosage and administration, relative contraindications, and clinically significant drug interaction of Phenobarbital. Although approved for the symptomatic management of anxiety disorders, the barbiturates, including phenobarbital, are not generally recommended for this indication because of the availability of benzodiazepines. Safety and efficacy of phenobarbital pharmacotherapy for women who are breast-feeding and their neonates and infants have not been established. Phenobarbital is excreted in sufficient quantities in breast milk to cause drowsiness and lethargy among nursing neonates and infants. Some injectable formulations of phenobarbital contain sodium bisulfite. Sulfites may cause hypersensitivity reactions, including anaphylactic reactions, among susceptible patients. The exact mechanism of phenobarbital’s CNS depressant action has not been fully determined. Phenobarbital appears to act primarily at the level of the thalamus, where it interferes with impulse transmission to the cortex.