Phenobarbital

General

• Type: Anticonvulsant, barbiturate, barbituates
• Dosage Forms
  • 65mg/mL injection
  • 20mg/5 mL oral solution
  • 15, 16.2, 30, 32.4, 60, 64.8, 97.2, 100mg tab

Adult Dosing

• Status epilepticus
  • 20mg/kg, infuse at 50-100mg/min
  • May repeat once after 10 minutes with additional 5-10mg/kg
• Alcohol withdrawal / Delirium Tremens
  • Loading dose of 10 mg/kg combined with a standardized lorazepam-based alcohol withdrawal protocol decreases ICU admissions
  • 130-260mg IV q15-20 min
• Seizures, maintenance dose
  • 50-100mg bid-tid

Pediatric Dosing

• Status epilepticus
  • 20mg/kg over 10 minutes. May repeat full dose in 15 minutes
• Seizures, maintenance dose
  • ≤5 yo: 3-5mg/kg/day in 1-2 divided doses
  • Children > 5 yrs: 2-3mg/kg/day in 1-2 divided doses
  • Adolescents: 1-3mg/kg/day in 1-2 divided doses

Special Populations

• Pregnancy Rating: D
• Lactation: Enters breast milk, use caution
• Renal Dosing
  • Adult
    • GFR < 10, give every 12-16 hours
    • HD: Given before HD and 50% dose after HD
  • Pediatric: GFR < 10, decrease dose by 50% and give every 24 hours
• Hepatic Dosing: Reduced dose recommended, but no defined protocols

Contraindications

• Allergy to class/drug
• Marked hepatic impairment
• Porphyria

Adverse Reactions

Serious

• Hypotension
• Respiratory depression, apnea
• Significant soft tissue injury with subcutaneous or intra-arterial administration
• Agranulocytosis

Common

• Sedation, respiratory depression

Pharmacology

• Onset: Oral 20-60 min, IV 5 min
• Peak: IV 30 min
• Half-life: Neonates 45-500 hr, Infants 20-133 hr, Children 37-73 hr, Adults 53-140 hr
• Metabolism: Hepatic
• Excretion: Urine
• Mechanism of Action: Barbituates

See Also

• Barbituates
• Alcohol withdrawal
• Status epilepticus

External Links

ACEP: Phenobarbital for Alcohol Withdrawal

References

• Lexicomp, UpToDate