Major, well-controlled trials of Vigabatrin for infantile spasms in Europe, Canada, and the Unites States are reviewed, including dose recommendations. Effective dosages ranged from 100 to 150 mg/kg/day, decreasing or eradicating spasms and eliminating the hypsarrhythmic EEG in newly diagnosed patients. Studies demonstrated long-term seizure control with no adverse effect on development and few severe adverse effects. Visual field defects were not evaluated. Time to response was within 2 weeks of initiating treatment. If the infant has not shown clinical improvement in 2 weeks, vigabatrin is discontinued and alternate treatment initiated. Treatment duration up to 6 months controlled seizures while limiting potential risks of adverse events and seizure recurrence.
A randomized, comparative trial of vigabatrin (150 mg/kg/day) and hydrocortisone (15 mg/kg/day) in 22 patients with tuberous sclerosis, found vigabatrin more efficacious and better tolerated than hydrocortisone, with 100% response during this 1- to 3-month crossover trial. Vigabatrin is recommended as first-choice treatment of infantile spasms caused by tuberous sclerosis.
In the UK Infantile Spasm Study comparing vigabatrin (100-150 mg/kg/day) with hormonal treatment (oral prednisolone 40-60 mg/day, or intramuscular tetracosactide 0.5-0.75 mg [40-60 IU], a synthetic analog of ACTH, on alternate days), hormonal treatments were superior to vigabatrin in control of spasms; adverse events were common with both forms of therapy. Hormonal treatment was preferred over vigabatrin. Infants with tuberous sclerosis were excluded from this study. Follow-up studies at age 14 months and 4 years indicated equivalent spasm-freedom and developmental outcomes with vigabatrin and hormone treatment, except for infants with cryptogenic spasms; infants with no identified etiology for spasms had higher developmental scores following hormone therapy.
Except for the UK study, all investigators preferred vigabatrin as first-line therapy over hormonal. The most common adverse events with vigabatrin were sedation and irritation. Delay in time to diagnosis and treatment is associated with less favorable outcomes. 
COMMENT. Vigabatrin is an irreversible GABA inhibitor, effective as adjunctive therapy in control of refractory complex partial seizures in adults and as monotherapy for infantile spasms. Clinical benefits of vigabatrin must be balanced with associated risk of peripheral visual field defects (pVFDs) . Field defects are bilateral and more pronounced nasally. Reported estimates of pVFDs are 30-50% in adults and 20% in children. Risk increases with increased dosage and duration of therapy. Vision screening is recommended at baseline, every 3 months, and at 3-6 months after discontinuation of therapy.