About Phenobarbitone Barbiturate derivative, Sedative-Hypnotic,Anticonvulsant. Mechanism of Action of Phenobarbitone Sedative and antiepileptic actions: Phenobarbitone mainly acts on Picrotoxin site of GABA -BZD receptor Cl- (chloride ion) channel complex. It prolongs the duration of GABA induced chloride channel opening and produces hyperpolarisation and decreases firing rate of neurons. This will alters the normal body functions. Phenobarbitone also has GABA mimetic action. At high concentrations Phenobarbitone directly increases chloride ion conductance and decreases transmission of calcium ion (Ca2+ ) dependent neurotransmitters. Phenobarbitone also inhibits excitatory glutamate neurotransmitters. At high concentration it also inhibits sodium ion channel and potassium ion channel. Phenobarbitone is used as an antiepileptic to control partial and generalised tonic-clonic seizures. Barbiturates activate inhibitory GABA-A receptors and inhibit excitatory AMPA receptors and produc