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Barbiturate Anticonvulsant Pregnancy: Avoid if possible — increased risk of congenital abnormalities; folic acid supplementation essential; neonatal coagulation defects (vitamin K prophylaxis for neonate at birth)

Phenobarbital (Paediatric Epilepsy — Beyond Neonatal)

Brand names: Phenobarbital (generic)

Adult dose

Dose: Loading (SE): 10–20 mg/kg IV at ≤100 mg/min. Maintenance: 60–180 mg OD oral
Route: IV or oral
Frequency: OD maintenance
Max: 600 mg loading; 240 mg/day maintenance
Adult SE loading: 10–20 mg/kg IV at max 100 mg/min

Paediatric dose

Dose: 20 mg/kg
Route: IV slow (≤1 mg/kg/min, max 100 mg/min)
Frequency: Loading: single dose. Maintenance: 2.5–5 mg/kg/day OD
Max: 1000 mg loading (PALS); 200 mg/day maintenance
Concentration: 30 mg/mL or 60 mg/mL injection; 15 mg/5 mL oral elixir mg/ml
BNF for Children / PALS: status epilepticus loading 20 mg/kg IV at ≤1 mg/kg/min (max 100 mg/min). Maintenance: 2.5–5 mg/kg/day OD oral/IV. Therapeutic level: 15–40 mg/L. Neonatal SE: see phenobarbital-neonatal entry. Controlled drug (CD). Source: BNF for Children 2024; PALS Advanced Life Support; NICE NG217

Dose adjustments

Renal

No dose adjustment required for mild-moderate renal impairment

Hepatic

Reduce dose in hepatic impairment — increased effect

Paediatric weight-based calculator

BNF for Children / PALS: status epilepticus loading 20 mg/kg IV at ≤1 mg/kg/min (max 100 mg/min). Maintenance: 2.5–5 mg/kg/day OD oral/IV. Therapeutic level: 15–40 mg/L. Neonatal SE: see phenobarbital-neonatal entry. Controlled drug (CD). Source: BNF for Children 2024; PALS Advanced Life Support; NICE NG217

Clinical pearls

  • Cognitive impairment: major concern in children — phenobarbital can impair cognitive development; avoid as first-line if alternatives available
  • Enzyme induction: reduces efficacy of many drugs including OCP (contraceptive counselling needed)
  • Vitamin D supplementation: recommended with long-term use to prevent metabolic bone disease
  • Withdrawal: must taper slowly — abrupt withdrawal can precipitate seizures

Contraindications

  • Porphyria
  • Respiratory failure (without mechanical support)
  • Severe hepatic impairment

Side effects

  • Sedation
  • Hyperactivity/paradoxical excitement (children)
  • Cognitive impairment and learning difficulties
  • Rickets/osteomalacia (long-term — CYP enzyme induction, vitamin D metabolism affected)
  • Ataxia
  • Nystagmus

Interactions

  • Multiple CYP inducers — reduces levels of warfarin, OCP, lamotrigine, phenytoin, valproate, other antiepileptics
  • Valproate — increases phenobarbital levels (competition)
  • Clonazepam — additive sedation

Monitoring

  • Plasma phenobarbital levels (target 15–40 mg/L)
  • Cognitive development in children (annual review)
  • Vitamin D and bone density (prolonged use)
  • Drug interactions

Reference: BNF for Children; NICE NG217 Epilepsy; PALS Advanced Life Support Manual. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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