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Vigabatrin

 

Usage

  • Vigabatrin is a potential treatment for epileptic spasms.
  • It is a first line therapy for the treatment of epileptic spasms due to Tuberous Sclerosis.
  • It is also a potential treatment for focal seizures or secondarily generalised seizures that have not responded to other medication including in patients with Tuberous Sclerosis.

 

Side effects

Common side effects:

  • Somnolence/sedation (rarely Vigabatrin may cause encephalopathic symptoms)
  • Weight gain
  • Dizziness
  • Double vision
  • Fatigue
  • Headaches
  • Nausea and abdominal pain
  • Behavioural disturbance (excitation/agitation/irritability)
  • Cognitive change  (thought disturbance/psychosis)

 

Other notable side effects:

  • Peripheral visual field loss: Vigabatrin is associated with a high incidence of visual field constriction. This is usually irreversible. Regular monitoring is required using ERG/perimetry according to age. The risk-benefit ratio of Vigabatrin usage must be discussed in this regard.
  • MRI abnormality: Vigabatrin may cause prominent signal abnormality in basal ganglia and upper brain stem, especially in infants. These abnormalities are usually reversible and may even remit with continued drug usage.
  • Rarely: Optic neuritis, rash, urticaria and angioedema.
  • All anticonvulsants are potentially teratogenic and this is often dose related (see section: Pregnancy and AEDs)
  • For a complete list of adverse effects, appropriate formularies should be consulted.

 

DOSING

  • The initiation and escalation dose depends upon age, weight, syndrome, seizure frequency and intensity, and side effect profile.
  • Unfortunately, a one dose regime does not fit all. A Paediatric Neurologist should be consulted if there is uncertainty.

 

 

A commonly used regime is below

  • Initial dose (Infantile spasms): 25mg/kg bd. The dose may be increased by 25-50mg/kg/day at intervals (for example, every 2-3 days depending upon response). In the UKISS study, dosage was increased up to 150mg/kg/day.
  • Initial dose (Adjunctive treatment for focal seizures): 10-20mg/kg/day given in two divided doses, then increase over 2-3 weeks to maintenance dose.
  • Gradual escalation to maintenance dose depends on efficacy and tolerance. Aim is to achieve the lowest possible efficacious dose, particularly to avoid side-effect of peripheral field restriction.  Discussion with neurologist is suggested in usage for focal seizures, particularly above dosages of 40-50mg/kg/day. Regular visual field surveillance is mandatory.
  • If the patient does not respond to Vigabatrin after a period of, for example, 3 months, withdrawal is suggested to avoid visual field abnormality.
  • Vigabatrin can be taken with or without food
  • Dosages per kilogram can only be used in children of weight approximately up to 30-40kgs. Consult appropriate formularies for higher weights and in the adult range.
  • These dosages are only a guideline and appropriate formularies should be consulted as needed

 

Weaning

  • When ceasing Vigabatrin it is recommended to reduce gradually (over a minimum of 2-4 weeks) to minimise the risk of increased seizure frequency or status epilepticus.

 

Preparations

  • 500mg tablets
  • 500mg sachets – dissolve in 10mL water.

 

Precautions

  • Use with caution in patients with a history of behavioural problems, depression or psychosis.
  • Vigabatrin may worsen absence and myoclonic seizures.
  • Renal impairment: As Vigabatrin is renally excreted, consult formularies and neurology.

 

Pregnancy

  • Usage in pregnancy needs to be discussed with a neurologist.
  • There is limited data on the safety of Vigabatrin in pregnancy.
  • All anticonvulsants are potentially teratogenic and this is often dose related (see section: Pregnancy and AEDs)

 

 

MIMS

PBS

 

 

Parent Handout

 

 

This page was last reviewed in May 2018.