428. Electroencephalographic abnormalities in patients with clozapine

Abstract

Convulsions are one of the serious side effects of clozapine. The aim of this study was to investigate the EEG abnormalities in patients treated with clozapine and elucidate the clinical significance of EEG changes concerning the therapeutic response and development of seizure. Fifty-nine patients were included in this study. Patients had standard 21-channel EEGs both before and during clozapine treatment. Clinical status of the patients was evaluated by GAF scores. Nine patients had abnormal baseline EEGs. All of them showed persistent abnormalities after clozapine treatment and three of them experienced seizures. Of the 50 patients who had normal baseline EEGs, 31 showed abnormal EEGs after clozapine treatment and two of them had seizures. Group differences in the prevalence were statistically significant for both EEG abnormalities and seizure. In those with normal baseline EEGs, most new-onset abnormalities occurred as nonspecific alterations such as slow wave and irregularity of posterior dominant rhythm. A positive correlation between the daily clozapine dosage and the amount of slow waves was found. Those who developed new-onset EEG abnormalities after clozapine treatment had a significantly greater improvement in GAF scores compared with patients with persistent normal EEGs. These results suggest that (1) a substantial proportion of patients treated with clozapine developed EEG abnormalities; (2) baseline EEG abnormalities would be a possible risk factor for clozapine-induced seizures; however, (3) new-onset EEG abnormalities after clozapine treatment may be a favorable factor for treatment response.