Clozapine is an atypical antipsychotic drug that is less likely to cause extrapyramidal side effects than classic neuroleptics. However, treatment with clozapine is associated with unusually high incidence of EEG abnormalities and with relatively high risk of epileptic seizures [26]. Clinical importance of EEG alterations during treatment with clozapine has been discussed for many years [3, 8, 23, 24, 32]. The aim of our study is to follow EEG changes in different stages of treatment with clozapine and to find out, whether there are some important correlates between EEG alterations and clinical data. In a group of 65 patients (18–59 y, 37 M, 28 F) in a different stages of treatment with clozapine (daily doses 25–699 mg) routine awake EEG recordings were performed. EEG were classified as normal (13 records) or abnormal. Abnormal tracings were subdivided as follows: 1. Bilateral or generalized slowing (25 records). 2. Paroxysmal – bilateral or generalized – slow activity (17 records). 3. Sharp waves or complexes of spikes/sharp waves and slow waves (10 records). EEG abnormalities were more frequent in patients with higher doses of clozapine (> 300 mg/d), but developed even at the begining of therapy (in one patient at daily dose of clozapine 25 mg). None of the patients suffered from ictal events. Our results suggest that EEG changes during clozapine treatment are influenced not only by clozapine itself, but other factors may play a role.

        Key words: pharmacotherapy, clozapine, EEG.