The side effects of clozapine may affect the treatment process negatively, and increase the disability.

We aimed to assess the side effects of clozapine, and their relationship with the clinical variables in schizophrenia patients, and study the predictors of disability.

Consecutive 122 outpatients who met DSM-IV criteria for schizophrenia, and were on clozapine treatment were included in the study. Information about sociodemographic characteristics, past and current clinical status were gathered through a clinical interview and review of the medical records, and physical measures and laboratory tests, including clozapine plasma levels, were recorded. The patients were assessed with SCID-I, Positive and Negative Syndrome Scale, UKU-Side Effect Rating Scale, WHO-Disability Assessment Schedule-II.

Hypersalivation, weight gain, sedation and constipation were the most common side effects of clozapine. Although the mean plasma clozapine levels were high (828.11±445.5ng/mL), no significant effect of clozapine dose and plasma levels were detected on the severity of side effects, except for constipation. Metabolic syndrome prevalence was found to be 50% according to ATP IIIA criteria. Duration of clozapine treatment, clozapine dose and plasma levels were not significantly different between patients with and without metabolic syndrome. Regression analysis showed that the severity of schizophrenia psychopathology and the number of side effects predicted the severity of disability.

Side effects of clozapine increase the disability of patients with schizophrenia and should be monitored regularly. On the other hand, clozapine dose and plasma levels do not determine the severity of most of the common side effects.