Phenobarbital is used as-
- Sedative and hence it relieves anxiety, tension and fear
- Hypnotic and hence it is used for short term insomnia
- Anti-epileptic in epilepsy with Partial seizure or Generalized Tonic-clonic seizure, status epilepticus
- Certain acute convulsive episodes
Phenobarbital is a long-acting barbiturate. It depresses the sensory cortex, reduces motor activity, changes cerebellar function and produces drowsiness, sedation and hypnosis. Its anticonvulsant property is exhibited at high doses.
Phenobarbital acts on GABAA receptors, increasing synaptic inhibition. This has the effect of elevating seizure threshold and reducing the spread of seizure activity from a seizure focus. Phenobarbital may also inhibit calcium channels, resulting in a decrease in excitatory transmitter release. The sedative-hypnotic effects of phenobarbital are likely the result of its effect on the polysynaptic midbrain reticular formation, which controls CNS arousal.
- Hypnosis: 100 to 320 mg
- Sedation: 30 to 120 mg/day in 2 to 3 divided doses
- Epilepsy: 60 to 250 mg/day
- Convulsion: 50 to 100 mg/day in 2 to 3 divided doses
- Status epilepticus: IV 10-20 mg/Kg, repeat if needed
- Preoperative: 1-3 mg/Kg body weight
- Convulsion: 4-6 mg/Kg/day
- Status epilepticus: IV 15-20 mg/Kg over 10-15 minutes