Vigabatrin (Sabril): An antiepileptic drug approved for the treatment of refractory complex partial seizures in adults and spasms in infants

New molecular entity: Vigabatrin (Sabril) was approved as an adjunctive treatment of refractory complex partial seizures in adults who have responded inadequately to several alternative treatments; and as monotherapy for pediatric patients with infantile spasms.

Vigabatrin tablets and powder for oral solution have been approved by FDA as an adjunctive treatment of refractory complex partial seizures (CPSs) in adults who have responded inadequately to several alternative treatments; and as monotherapy for pediatric patients with infantile spasms.

Efficacy. The efficacy of vigabatrin as adjunctive therapy in adult patients with CPS was established in 2 US-based, multicenter, double-blind, placebo-controlled trials. A total of 357 adults with CPSs, with or without secondary generalization, were enrolled. Patients were required to be on an adequate and stable dose of an anticonvulsant, and have failed an adequate regimen of carbamazepine or phenytoin. In these trials, patients taking vigabatrin experienced a significant reduction in mean monthly frequency of CPSs compared to placebo. A randomized, placebo-controlled trial enrolling 40 patients provides the best evidence establishing the efficacy of vigabatrin as monotherapy in infants with a confirmed diagnosis of infantile spasm. Patients receiving vigabatrin had a larger average percent reduction in daily spasm frequency than those receiving placebo.

Safety. Vigabatrin can cause progressive and permanent bilateral concentric visual field constriction in a high percentage (>30%) of patients, and in some cases, may reduce visual acuity. The risk increases with total dose and duration of use, and the timing is unpredictable. Consequently, vision testing at initiation and every 3 to 6 months is required. In addition to permanent vision loss, fatigue, somnolence, nystagmus, tremor, blurred vision, memory impairment, weight gain, arthralgia, abnormal coordination, and confusional state were common side-effects in adults. Somnolence, bronchitis, ear infection, and acute otitis media were most common in infants.