Phenobarbital Sodium (Phenobarbitone)

Phenobarbital Sodium (Phenobarbitone) - The bioavailability of Phenobarbital is 90%, so the IV dose can be regarded as the same as the oral dose.With a half-life of 1.4–4.9 days, steady-state may take 5–14 days to be reached.Therapeutic serum levels for seizures range from 10 to 40 mg/l although the optimal plasma concentration for some individuals may vary outside this range. Phenobarbital usually lowers phenytoin levels but they can also be increased. Laboratory levels may be reported in μmol/l or mg/l. To convert mg/l into μmol/l multiply by 4.31.

Uses
Status epilepticus
Contraindications
Porphyria

Administration
• IV: 10 mg/kg (maximum daily dose 1 g)
Dilute to 10 times its own volume with WFI immediately before
use. Give at < 100 mg/min

Phenobarbital can be continued at a rate of 50 mg/min until seizures cease;maximum cumulative dose in the absence of intubation, 20 mg/kg. Reduce dose and inject more slowly in the elderly, patients with severe hepatic and renal impairment, and in hypovolaemic and shocked patients. Maintenance dose: 1 mg/kg IV 12 hourly (average maintenance dose 30–60 mg 12 hourly).To discontinue therapy,wean off slowly over several weeks by reducing daily dose by 15–30 mg/day every fortnight. In obese patients, dosage should be based on lean body mass.

Adverse effects
Respiratory depression
Hypotension
Bradycardia
CNS depression

Organ failure
CNS: sedative effects increased
Respiratory: respiratory depression
Hepatic: can precipitate coma
Renal: reduce dose

Renal replacement therapy
No further dose modification is required during renal replacement therapy