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Antiepileptic — GABA Transaminase Inhibitor Pregnancy: Avoid — limited data; supplement folate

Vigabatrin

Brand names: Sabril

Adult dose

Dose: 1 g twice daily; increase by 500 mg/week; maintenance 2–3 g/day
Route: Oral
Frequency: Twice daily
Max: 3 g/day
Irreversibly inhibits GABA transaminase — increases brain GABA levels. Adjunctive therapy for refractory focal epilepsy. First-line for infantile spasms (West syndrome) in combination with pyridoxine. USE RESTRICTED — causes permanent visual field defects in 30–50% of adult patients.

Paediatric dose

Dose: 40–50 mg/day/kg
Route: Oral
Frequency: Twice daily
Max: 150 mg/kg/day
Infantile spasms (West syndrome): 50–150 mg/kg/day in 2 divided doses — first-line (with ACTH/corticosteroids). Focal epilepsy in children: 40–80 mg/kg/day.

Dose adjustments

Renal

Reduce dose: 50% reduction if eGFR 10–50; 75% if eGFR <10.

Hepatic

No specific adjustment.

Paediatric weight-based calculator

Infantile spasms (West syndrome): 50–150 mg/kg/day in 2 divided doses — first-line (with ACTH/corticosteroids). Focal epilepsy in children: 40–80 mg/kg/day.

Clinical pearls

  • Visual field defects are IRREVERSIBLE — monitor every 6 months with Goldmann perimetry. Discontinue if defects detected. Inform DVLA.
  • Infantile spasms: vigabatrin is first-line particularly for tuberous sclerosis — superior to corticosteroids in TSC-associated West syndrome
  • Risk-benefit: use only for West syndrome (infantile spasms) or refractory focal epilepsy where benefits outweigh the visual field risk

Contraindications

  • Pre-existing visual field defects
  • Patients unable to attend visual field monitoring

Side effects

  • Permanent visual field constriction (30–50% of adults — bilateral concentric narrowing)
  • Sedation
  • Weight gain
  • Behavioural disturbance (especially in children — agitation, aggression)
  • MRI signal changes (infantile spasms — reversible)

Interactions

  • Phenytoin (reduces phenytoin levels by 20–30%)
  • Clonazepam (additive CNS depression)

Monitoring

  • Ophthalmology visual field assessment every 6 months (Goldmann perimetry)
  • Seizure control
  • Behavioural assessment in children

Reference: BNFc; BNF 90; NICE NG217; BNFc; MHRA Vigabatrin Visual Field Guidance. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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