Clinical predictors of therapeutic response to clozapine in a sample of Turkish patients with treatment-resistant schizophrenia

Abstract

Background Several lines of evidence suggest that clozapine is more effective than both first- and second-generation antipsychotic drugs in treatment-resistant schizophrenia (TRS). However, clinicians appear to be hesitant to prescribe this drug. It would therefore be extremely valuable if predictors of response to clozapine could be identified. The aim of this study was to evaluate the predictive factors of clinical responses to clozapine in a group of Turkish patients with TRS. Methods This was a 16-week uncontrolled open study carried out among 97 TRS patients (80 males and 17 females; DSM-IV diagnosis). All patients fulfilled the criteria for refractory schizophrenia according to the UK guidelines for the National Institute of Clinical Excellence (NICE). After all previous antipsychotic medications had run their course, the patients were started on clozapine according to a standardized titration and dosage schedule. Psychopathology was evaluated before the initiation of clozapine therapy and once every 4 weeks using the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment for Positive Symptoms, and the Scale for the Assessment of Negative Symptoms. Results Of the TRS patients on clozapine, 55.7% achieved a clinical response, defined as at least a 20% decrease in BPRS. We observed a favorable effect of clozapine on both positive and negative symptoms. Logistic regression analysis showed that a good clozapine response was more likely when schizophrenia began at a later age, when negative symptoms were severe, and when patients had an early response at 4 weeks. Conclusion A combination of demographic, baseline clinical, and acute treatment response variables may accurately predict response to clozapine in TRS. Priority should be given to initiating clozapine at the earliest phase of TRS, especially for patients with evident negative symptoms.