A hydantoin anticonvulsant; inhibits voltage-gated sodium channels in a voltage-dependent manner; suppresses the persistent sodium current in a dose-dependent manner (10-100 μM) in neurons isolated from rat neocortex; reduces seizure frequency and duration by 46 and approximately 20%, respectively, when administered over 7 days (75 mg/kg, i.p., the first day, then 50 mg/kg per day) in a rat model of status epilepticus; oxidized by cytochrome P450 into products that can lead to cell death in vitro and toxic effects in vivo, such as gingival hyperplasia and teratogenicity in rats and mice, respectfully