Phenobarbital is an effective and safe anticonvulsant drug introduced in clinical use in
1904. Its mechanism of action is the synaptic inhibition through an action on GABAA. The loading
dose of phenobarbital is 20 mg/kg intravenously and the maintenance dose is 3 to 4 mg/kg by mouth.
The serum concentration of phenobarbital is up to 40 g/ml. Nonresponders should receive additional
doses of 5 to 10 mg/kg until seizures stop. Infants with refractory seizures may have a serum concentration
of phenobarbital of 100 g/ml. Phenobarbital is metabolized in the liver by CYP2C9 with minor
metabolism by CYP2C19 and CYP2E1. A quarter of the dose of phenobarbital is excreted unchanged
in the urine. In adults, the half-life of phenobarbital is 100 hours and in term and preterm infants
is 103 and 141 hours, respectively. The half-life of phenobarbital decreases 4.6 hours per day and it is 67 hours in infants
4 week old.
Keywords: Dosing, metabolism, neonate, pharmacokinetics, phenobarbital, serum-levels.
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