The response rate to clozapine in patients with treatment-resistant schizophrenia spectrum disorders (TRSS) is around 40 %. But, in general, a better prognosis is noted for schizophrenia in developing countries, including India. Given the scarcity of related literature from India, this study aimed to evaluate the response rates to clozapine in TRSS and explore predictors of response. Sociodemographic and clinical information from randomly selected 250 patients on clozapine for TRSS was collected through a retrospective chart review. Clozapine response was determined using the Clinical Global Impression-Schizophrenia scale at 6, 12, 24 weeks, and one year of initiating clozapine. Elastic net logistic regression analysis was performed to identify predictors of clozapine response. A total of 54 % responded to clozapine, with much or very much improvement in positive and overall symptoms of schizophrenia by the end of 12 weeks of clozapine initiation. Among all the responders at 12 weeks, 94 % continued to maintain response at one-year follow-up, and among non-responders, 34.2 % showed clinical improvement by 1-year follow-up. Lower symptom severity at baseline, good response to clozapine at six weeks, history of more suicidal attempts, and few other clinical symptoms like delusions and sociodemographic factors predicted a response to clozapine. A higher response rate (54 %) to clozapine is noted in 3rd month of clozapine, contrasting with the existing literature. Persistence of treatment could elicit further response over a year in early non-responders. Our study findings revealed that the demographic profile and clinical determinants may have an effect on clozapine response.
Keywords: Clinical outcome; Clozapine-resistance; Response prediction; Ultra-resistance.
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