Infantile spasms usually start during the first year of life and constitute one of the most difficult types of epilepsy to treat. They carry a very poor prognosis for both epilepsy and mental development. Seventy children, including 47 infants, with intractable infantile spasms were entered into an open study with vigabatrin as add-on therapy to the usual anticonvulsant treatment. All were resistant to previous treatments, including corticosteroids (43 patients), carbamazepine, benzodiazepines, and sodium valproate. Two children withdrew from the study because of intolerance to vigabatrin (hypotonia or hypertonia) before evaluation of efficacy could be made. Of the remaining 68 children, 29 (43%) showed complete suppression of spasms. Forty-six children had a greater than 50% reduction in spasms. The best response was observed in those with tuberous sclerosis (12/14 compared with 12/18 with symptomatic infantile spasms of other origin and 22/36 with cryptogenic infantile spasms). Following the initial response to treatment of these patients (n = 68), a long-term response was confirmed in 75% of children with symptomatic infantile spasms and 36% of children with cryptogenic infantile spasms. In eight children, all other anticonvulsant medication could be definitively withdrawn. Tolerability appeared excellent, with 52 of 70 patients reporting no side effects. Somnolence, hypotonia, weight gain, excitation, and insomnia were the most common problems at the beginning of the study and were usually transient. Given the poor prognosis of this type of childhood epilepsy, vigabatrin appears to be a very interesting advance in the management of drug-resistant infantile spasms. (J Child Neurol 1991;6(Suppl):2S52-2S59).

1. The pharmacokinetics of the enantiomers of vigabatrin were investigated after oral administration of a single 50 mg kg‐1 dose of the racemate to two groups of six epileptic children (I: 5 months‐2 years, II: 4‐14 years). 2. The mean (+/− s.d.) values of maximum plasma concentration and area under the plasma concentration‐time curve of the R(‐) enantiomer were significantly higher than those of S(+) vigabatrin in both groups: R(‐) Cmax: 21 +/− 6.6 (I)‐41.3 +/− 13.9 (II) vs S(+) Cmax: 13.9 +/− 4.5 (I)‐23.8 +/− 12.2 (II) mg l‐1; R(‐) AUC: 106 +/− 28.5 (I)‐147 +/− 34 (II) vs S(+) AUC: 90.9 +/− 27.9 (I)‐117 +/− 26 (II) mg l‐1 h. In group I, the half‐life of the R(‐) isomer was significantly shorter than that of the S(+) isomer; in group II, the half‐lives were comparable. 3. For the R(‐) enantiomer the area under the curve, and the elimination half‐life increased linearly with age. 4. During chronic administration (50 mg kg‐1 vigabatrin racemate twice a day for 4 days), the morning trough plasma drug concentrations did not increase.

Sixty-one pediatric patients (12-229 months of age) with refractory epilepsy were treated with vigabatrin [gamma-vinyl GABA (GVG)] in a 16-week, single-blind, add-on, placebo-controlled trial. Twenty-three patients (38%) showed a reduction of more than 50% in seizure frequency; 12 patients (20%) experienced a seizure increase; and the remaining 26 did not show significant differences between placebo and GVG treatment. Among the 216 patients who entered the long-term phase after having experienced more than 50% decrease in seizure frequency, 14 continued with the same degree of improvement after 2-11 months of follow-up (mean 7.7). GVG was particularly efficient in cryptogenic partial epilepsy. Conversely, nonprogressive myoclonic epilepsy tended to be aggravated. Agitation was the most commonly observed side effect, mainly at onset of therapy in mentally retarded patients, but was easily reversed by dose reduction. GVG is a promising drug in the treatment of refractory epilepsies of childhood.

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Sixty-six children with various types of severe drug-resistant epilepsy were entered into a long-term, dose-rising study of vigabatrin after a 4-week run-in placebo period. All the children were receiving one to three other antiepileptic drugs, the doses of which were not changed during the 6-month dose titration phase. Following the introduction of vigabatrin, 11 patients became seizure free, and 28 responded with a greater than 50% reduction in seizure frequency. The following types of epilepsy responded favorably in order of decreasing efficacy: cryptogenic and symptomatic partial epilepsy, other symptomatic generalized epilepsy, and Lennox-Gastaut syndrome. However, three of nine patients with myoclonic epilepsy showed an increase in seizure frequency. Optimal responses were found with vigabatrin doses of 40 to 80 mg/kg/ day, although no significant adverse effects were noted with doses of higher than 100 mg/kg/day. Thirty-eight responders continued on vigabatrin, 19 of whom have been treated for more than 1 year, with generally good efficacy. As a result of discontinuing concomitant antiepileptics, six patients are on monotherapy with vigabatrin, four of whom are seizure free. Vigabatrin tolerability was good, with 39 of 66 children reporting no adverse effects. Hyperkinesia was reported in 17 patients (26%), and two had to drop out of the study. All these patients had a history of hyperkinesia or mental retardation. In patients in whom vigabatrin dose was reduced because of hyperkinesia, a dose increase could later be instituted without recurrence of symptoms. There was no change in neurologic examination and no drug-related abnormalities in clinical laboratory data. It is concluded that this study shows that vigabatrin is safe and effective in the treatment of refractory epilepsy of various types in children. The recommended starting dose is 40 mg/kg/day, which can be increased up to 80 mg/kg/day, depending on clinical response. (J Child Neurol 1991;6(Suppl):2S30-2S37).