Level 3

barbituric acid derivative

- long-lasting barbiturate and anticonvulsant used in the treatment of all types of seizures, except for absent seizures
- Sedation
- sometimes used for alcohol detoxification and benzodiazepine detoxification for its sedative and anti-convulsant properties

Tablets.
IV solution either 65mg or 130mg/1ml

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.

- depresses the sensory cortex, decreases motor activity, and alters cerebellar function.
- also capable of producing a dose-dependent respiratory depression

causes few systemic side effects, but its use is limited mainly due to the high rate of sedation and cognitive impairment.

Toxicity:
- CNS and respiratory depression which may progress to Cheyne-Stokes respiration, areflexia, constriction of the pupils to a slight degree (though in severe poisoning they may show paralytic dilation)
- oliguria, tachycardia, hypotension, lowered body temperature, and coma.
- Typical shock syndrome (apnea, circulatory collapse, respiratory arrest, and death) may occur.

Variable rates of absorption

20 to 45%

not available

Hepatic (mostly via CYP2C19).

20-40% unchanged in urine

50-160 hours

Status:
Loading 15-20mg/kg
Maintenance 2mg/kg/day in divided doses

barbituric acid derivative

Sedative / Hypnotic

Anticonvulsant
Sedative-Hypnotic