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Medical and Pharmacy Editor:

Brand Name: N/A

Generic Name: Phenobarbital

Drug Class: Anticonvulsants, Barbiturates

What Is Phenobarbital and How Does It Work?

Phenobarbital is used alone or with other medications to control seizures. Controlling and reducing seizures lets you do more of your normal daily activities, reduces your risk of harm when you lose consciousness, and lessens your risk for a possibly life-threatening condition of frequent, repeated seizures. Phenobarbital belongs to a class of drugs known as barbiturate anticonvulsants/hypnotics. It works by controlling the abnormal electrical activity in the brain that occurs during a seizure. Phenobarbital is also used for a short time (usually no more than 2 weeks) to help calm you or help you sleep during periods of anxiety. It works by affecting certain parts of the brain to cause calming.

Dosages of Phenobarbital

Dosage Forms and Strengths

Tablet: Schedule IV

  • 15 mg
  • 16 mg
  • 30 mg
  • 32 mg
  • 60 mg
  • 64.8 mg
  • 65 mg
  • 100 mg

Elixir: Schedule IV

  • 20 mg/5mL

Injectable solution: Schedule IV

  • 30 mg/mL
  • 60 mg/mL
  • 65 mg/mL
  • 130 mg/mL

Dosage Considerations – Should be Given as Follows:

Status Epilepticus

  • Typically used after benzodiazepines and phenytoin fail to abort status epilepticus
  • Adult: 15-18 mg/kg intravenous (IV) loading dose infused at 25-60 mg/min; prepare to support ventilation; may repeat in 20-minute intervals as needed; not to exceed 30 mg/kg
  • Infants and children: 15-20 mg/kg IV infused at a rate not to exceed 2 mg/kg/min; not to exceed 1000 mg/dose
  • Children under 60 kg: IV rate at less than 30 mg/min
  • May repeat with 5-10 mg/kg bolus dose after 15-30 min as needed; not to exceed cumulative dose of 40 mg/kg


  • All types of seizure disorders, including partial, tonic-clonic, and myoclonic seizures
  • Adult: 1-3 mg/kg/day oral/intravenous (IV) in 1-2 divided doses initially; adjust accordingly to maintain within therapeutic serum concentration range
  • Neonates (less than 28 days): 3-5 mg/kg/day intravenously (IV)/orally in 1-2 divided doses
  • Infants: 5-6 mg/kg/day intravenously (IV)/orally in 1-2 divided doses
  • Children 1-5 years: 6-8 mg/kg/day intravenously (IV)/orally in 1-2 divided doses
  • Children 6-12 years: 4-6 mg/kg/day intravenously (IV)/orally in 1-2 divided doses
  • Children over 12 years: 1-3 mg/kg/day intravenously (IV)/orally in 1-2 divided doses, OR 50-100 mg two or three times daily


  • Adult: 30-120 mg/day orally divided two or three times daily; do not exceed 400 mg/day
  • Pediatric: 2 mg/kg orally three times daily


  • Adult: 100-320 mg/day orally/intravenously/intramuscularly; do not administer for more than 2 weeks
  • Pediatric: 3-5 mg/kg orally at bedtime


  • 100-200 mg orally at bedtime; do not exceed 400 mg/day

Preoperative Sedation, Pediatric

  • 1-3 mg/kg orally/intravenously/intramuscularly 1-1.5 hours before procedure

Hyperbilirubinemia (Off-label), Pediatric

  • Neonates: 5 mg/kg/day orally/intravenously (IV) once/day, OR divided every 12 hours for 3-6 days following birth
  • Children under 12 years (chronic cholestasis): 1.5-4 mg/kg orally every 12 hours

Dosing Considerations

  • Antiepileptic therapeutic concentration range: 10-40 mcg/L (43-172 micromoles/L)
  • Long half-life permits once-daily dosing, if tolerated, for seizures; single daily dosing at bedtime recommended because of sedation
  • Children under 6 years: Potential toxic dose 8 mg/kg
  • Pediatric: Antiepileptic therapeutic concentration range: 15-30 mcg/L (43-129 micromoles/L)
Medically Reviewed by a Doctor on 1/10/2018


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