Abstract
Objectives: The aim of this study was to investigate any possible additional effects of long-term use of clozapine and to figure out the factors related to additional improvement after 6 months.
Methods: 31 inpatients with schizophrenia who have taken clozapine over 1 year were recruited, and changes of their symptom severity were assessed with Brief Psychiatric Rating Scale-18(BPRS-18) at the baseline, 6 weeks, 6 months, and 12 months after the baseline. Changes of BPRS-18 scores across time were analyzed by repeated measure ANOVA. To identify which factor is related to additional improvement with long-term use of clozapine, subjects were classified into 2 groups; clozapine-responsive group and clozapine-resistant group. And logistic regression was performed for two groups.
Results: The analysis revealed the significant improvements of BPRS-18 scores had continued until 6 month, but no significant change found at 12 month. The greatest change of BPRS-18 score was observed at 6 week. Clozapine responsive group(n=14) seemed to have later onset time of the disease, get longer years of education, take more doses of clozapine, and show worse conditions in BPRS-18 at baseline than clozapine resistant group did. However, no significant differences in characteristics were found in logistic regression.
Conclusion: From the results above, some patients with chronic schizophrenia seem to benefit from maintaining clozapine over 6 months. Though no factors predictive of additional efficacy after 6 weeks of clozapine therapy were found, this work suggests it is worth maintaining clozapine over 6 months for some patients if there are no other probable options left in clinical setting.