Prevalence and pattern of electroencephalographic changes associated with clozapine treatment: a cross-sectional study

BackgroundClozapine is a second-generation antipsychotic which is known to have superior efficacy as compared to other antipsychotics. It is particularly used in treatment-resistant schizophrenia (10-30%). However, its use is limited due to the serious side effect of inducing seizures which can occur at all doses. The purpose of our study was to analyse patients taking clozapine for any electroencephalographic (EEG) abnormalities. We undertook a cross-sectional study on 107 patients with a different diagnosis taking clozapine who visited the outdoor treatment facility of a tertiary care psychiatric diseases hospital in Kashmir. A 32-channel digital EEG was obtained and evaluated visually for any abnormalities in these patients. The data was tabulated and analysed using SPSS 23.0.ResultsEEG abnormalities were reported in 60.75% of patients receiving clozapine out of which slow waves and epileptiform activities were present in 48.60% and 30.84% of patients, respectively. Background slowing was often in the delta and theta ranges. Our study showed that there was a statistically significant relationship between the dose of clozapine and EEG abnormalities. Clinical seizure occurred in only one patient receiving clozapine 450 mg/day and was a smoker who had recently stopped smoking.ConclusionsEEG abnormalities occur frequently in clozapine-treated patients specifically those taking higher doses of clozapine. This calls for utilising EEG as a useful clinical investigation in these patients along with clinical monitoring of seizures especially in those taking higher doses of clozapine in order to hint towards early signs of clozapine toxicity. Caution needs to be taken in patients who are smokers and show a pattern of change in their smoking habits. Moreover, EEG abnormalities though frequently associated with clozapine are not reliable predictors of seizures. Therefore, anticonvulsants may not be routinely indicated in patients on clozapine even in the presence of epileptiform discharges.