Effect size of symptom status in withdrawal of typical antipsychotics and subsequent clozapine treatment in patients with treatment-resistant schizophrenia

Objective: In light of the efficacy of newer antipsychotic agents and the possibility that drug withdrawal may negatively affect subsequent drug response, concern has arisen that the use of placebo in schizophrenia research may be unethical. This study examines the effect size of symptom exacerbation during drug washout with placebo and the effects of drug washout on the efficacy of subsequent drug treatment. Method: Fifty patients with treatment-resistant schizophrenia hospitalized on a research unit participated in a double-blind longitudinal study of the effects of drug washout after chronic treatment with a typical antipsychotic and before prospective treatment with clozapine. Brief Psychiatric Rating Scale (BPRS) scores were analyzed to examine drug effects and effect sizes for baseline treatment with a typical antipsychotic (>6 months treatment), drug washout with placebo (mean=34 days), early treatment with clozapine (mean=42 days, mean dose=345.0 mg/day), and optimal clozapine treatment (mean=83 days, mean dose=450.5 mg/day). Results: Patients' BPRS total, positive, and negative symptom scores significantly increased during placebo washout, compared with baseline treatment, and significantly decreased with administration of clozapine, compared with placebo washout and baseline treatment. However, 30% of patients showed some symptom improvement during placebo washout. The effect sizes for the BPRS total score were 0.63 for baseline treatment versus placebo washout, 1.10 for optimal clozapine treatment versus placebo washout, and 0.82 for optimal clozapine treatment versus baseline treatment. Conclusions: Symptom exacerbation induced by drug withdrawal in patients with treatment-resistant schizophrenia did not impede subsequent responsiveness to clozapine. The effect size for clozapine, compared with typical antipsychotics, suggests that the drug-washout longitudinal design is useful for establishing a drug-free baseline and for investigating drug response, while requiring relatively few subjects.