Incidence of seizures with phenytoin toxicity.

Among 50 patients with phenytoin intoxication, 14 had seizures during the episode. Seizures in 9 of these 14 patients probably resulted from poor seizure control despite high phenytoin levels, but in 5 cases, attacks were attributed to phenytoin toxicity. The only factor that seemed to correlate with seizures was a serum phenytoin level over 30 micrograms/ml. No demographic, metabolic, neuropsychiatric, or therapeutic variables were predictive; nor were any other symptoms of toxicity particularly likely to be found in association with seizures. Seizures are an occasional manifestation of phenytoin toxicity, particularly when levels are high.