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Therapeutic actionIndicationsForms and strengths, route of administrationDose and durationContra-indications, adverse effects, precautionsFAQs
1 May 2026Injectable drugsSource update: October 2024

Phenobarbital Infusion Dose for Seizures

Phenobarbital guidance for second-line treatment of convulsive status epilepticus.

Also searched as

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Prescription under medical supervision

Source reviewed

October 2024

Guide category

Injectable drugs

Safety boundary

Prescription medicine information for clinician-guided use.

Kenza Health Hub presents this medicine page as structured health education. Check dose, route, interactions, pregnancy or breast-feeding considerations, and local protocol with a qualified clinician or pharmacist. Read our medical editorial policy.

This guide page is for structured reference only and does not replace a clinician, pharmacist, or emergency review. Dose choice, route choice, interactions, and safety decisions still need professional judgment.

Therapeutic action

Antiseizure (anticonvulsant), sedative.

Indications

Second-line treatment of convulsive status epilepticus.

Forms and strengths, route of administration

During and after administration, have ventilation equipment and solutions for fluid replacement ready for use.

Do not exceed an infusion rate of 1 mg/kg/minute in children and 100 mg/minute in adults.

  • 200 mg in 1 ml ampoule (200 mg/ml) for IV infusion in 0.9% sodium chloride.
  • Do not administer by direct IV injection.
  • Do not administer the solution undiluted.
  • Do not administer by SC injection.

Dose and duration

Loading dose

  • Child 1 month and over: add 1 ml (200 mg) of PB to 9 ml of 0.9% sodium chloride to obtain 10 ml of solution containing 20 mg/ml. Administer 20 mg/kg, maximum 1 g, over 20 minutes by IV infusion using a syringe pump, or if not available, a paediatric infusion set.
  • If seizures do not stop after the first dose, readminister half-dose: 10 mg/kg.
  • Adult: 15 mg/kg, maximum 1 g, as a single dose over 15 minutes.
  • Use diluted solution as above if administered by syringe pump. Use undiluted solution if administered by IV infusion in a bag of 100 ml of 0.9% sodium chloride.
  • If maintenance treatment is indicated after the loading dose, change to oral route as soon as possible.

Contra-indications, adverse effects, precautions

  • Do not administer to patients with severe respiratory, renal, or hepatic impairment.
  • Administer with caution in children, older patients, and patients with mild to moderate respiratory, renal, or hepatic impairment.
  • May cause drowsiness, dizziness, headache, behavioural disturbances, dose-dependent respiratory depression, hypotension, apnoea, laryngospasm, shock, haematologic disorders, gastrointestinal disturbances, hypersensitivity reactions, and coma in overdose.
  • Monitor respiratory rate and blood pressure closely during and after administration.
  • Avoid or monitor combination with mefloquine, benzodiazepines, opioid analgesics, antipsychotics, first-generation antihistamines, antidepressants, and other antiseizure medications.
  • Use with extreme caution with benzodiazepines and opioid analgesics.
  • Phenobarbital may reduce the effect of many drugs including diazepam, midazolam, antimicrobials, some antiretrovirals, corticosteroids, tricyclic antidepressants, itraconazole, direct-acting antivirals for hepatitis C, and warfarin.
  • Implants and oral contraceptives: use condoms until next menstruation.
  • Pregnancy and breast-feeding: prefer a safer drug such as levetiracetam. If phenobarbital is the only option, the risks linked to status epilepticus appear greater than the risks linked to phenobarbital.
  • Phenobarbital is subject to international controls: follow national regulations.
  • Do not mix with other drugs in the same syringe or infusion.

Frequently Asked Questions

Phenobarbital = PB injectable dose and administration questions

What is phenobarbital injectable used for in seizures?

This guide lists phenobarbital injectable as second-line treatment of convulsive status epilepticus.

What is the phenobarbital dose for seizures?

For children 1 month and over, the listed loading dose is 20 mg/kg, maximum 1 g, over 20 minutes by IV infusion. If seizures do not stop after the first dose, the guide lists a half-dose of 10 mg/kg. For adults, it lists 15 mg/kg, maximum 1 g, as a single dose over 15 minutes.

How should phenobarbital IV infusion be prepared?

For children, the guide says to add 1 ml of phenobarbital 200 mg/ml to 9 ml of 0.9% sodium chloride to obtain 20 mg/ml, then administer by syringe pump or paediatric infusion set. Adult administration may use diluted solution by syringe pump or undiluted solution in a 100 ml bag of 0.9% sodium chloride.

What is the maximum phenobarbital infusion rate?

The guide says not to exceed 1 mg/kg/minute in children and 100 mg/minute in adults.

Source

MSF Essential drugs practical guidelines (January 2026)

This page combines source-derived medicine reference sections with Kenza editorial context, while leaving out the Storage and Remarks sections from the source batch.

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