ChEBI: Phenobarbital is a member of the class of barbiturates, the structure of which is that of barbituric acid substituted at C-5 by ethyl and phenyl groups. It has a role as an anticonvulsant, a sedative, an excitatory amino acid antagonist and a drug allergen.NCI Thesaurus (NCIt): Phenobarbital is a long-acting barbituric acid derivative with antipsychotic property. Phenobarbital binds to and activates the gamma-aminobutyric acid (GABA)-A receptor, thereby mimicking the inhibitory actions of GABA in the brain. The activation effects of the phenobarbital-receptor-ionophore complex include increased frequency of chloride channel openings, membrane hyperpolarization and ultimately synaptic inhibition and decreased neuronal excitability. In addition, this agent inhibits glutamate induced depolarization.