Valproic acid therapy for complex partial seizures. Its efficacy and toxic effects

Twenty-four adult outpatients with poorly controlled complex partial seizures were treated with valproic acid. Previous therapy with antiepileptic agents was continued to maintain stable plasma drug levels. Initially 12 patients experienced greater than 50% seizure reduction. Only five patients maintained longterm benefit. In the other seven patients a tolerance developed to valproic acid's efficacy. Duration of seizure control seemed to be a function of initial seizure frequency. Toxic effects were generally mild. No hepatotoxic effect was noted and no hematological abnormalities developed. Weight changes occurred in 17 patients (14 gained weight) and five patients experienced a postural tremor. Eighteen patients experienced nausea.