Purpose: Clozapine has been reported to be effective for refractory schizophrenic patients. However, there have been few reports investigating whether clozapine responders are likely to suffer from more or fewer extrapyramidal symptoms. The aim of the present study is to investigate the association between clinical effects of clozapine and extrapyramidal symptoms in clozapine-treated patients.
Methods: Ten patients were divided into Improvement Group with CGI-I scores ranging from 1 to 3 and Non-improvement Group with CGI-I scores ranging from 4 to 7. The Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS) scores were compared between these two groups just before starting clozapine treatment and after 12 weeks of clozapine treatment.
Results: Although there was no significant difference in any DIEPSS scores between Improvement Group and Non-improvement Group just before clozapine treatment, Improvement Group had significantly fewer extrapyramidal symptoms in DIEPSS scores than Non-improvement Group after 12 weeks of clozapine treatment. Moreover, there was a significant interaction between overall severity of extrapyramidal symptoms assessed by DIEPSS and improvement measured by CGI-I across the 12 weeks of clozapine treatment.
Discussion: These findings suggest that clozapine responders are less likely to suffer from extrapyramidal symptoms.