A retrospective study of clozapine and electroencephalographic abnormalities in schizophrenic patients.

This study investigated the incidence and nature of clozapine-associated electroencephalographic (EEG) abnormalities and the relationship between EEG abnormality and clozapine dosage in Korean schizophrenic patients. Fifty schizophrenic patients with normal baseline EEG and with additional EEG record examined during clozapine treatment more than once were included. Thirty-one patients (62%) showed abnormal EEGs after clozapine treatment, and two of them had seizures. The majority of EEG abnormalities presented as nonspecific slow waves (SW). Spikes (or spike and wave complexes; SP) and frontal intermittent rhythmic delta activity (FIRDA) were relatively rarely observed. The probability of EEG abnormality was linearly dependent on the daily dose of clozapine and patient's age. Our results can be summarized as follows: (1) a substantial proportion of Korean patients treated with clozapine develops EEG abnormalities, and its incidence is comparable to the published results in Caucasian patients; (2) EEG abnormalities occurred in a dose-dependent manner; and (3) the occurrence of EEG abnormalities did not necessarily lead to future seizure development, except in a small number of cases.