Antipsychotic switching: results from a one-year prospective, observational study of patients with schizophrenia

Objective: The Health Outcomes of a Canadian Community Cohort (HOCCC) study is a 1-year prospective observational study of outpatients with schizophrenia or related psychotic disorders. The purpose of the study was to compare effectiveness of antipsychotic treatment as measured by 1-year treatment completion rates. Design and methods: Patients (N = 929) were enrolled if in the course of usual clinical practice they switched to a second-generation antipsychotic (SGA). Observational data were collected for up to 1 year. The primary analysis compared 1-year treatment-completion rates for the olanzapine cohort with the other SGA cohort (quetiapine, risperidone, clozapine), using a chi-squared test. Results: Of 929 patients enrolled, 64.8% (516/796) of evaluable patients completed 1 year of treatment. There was no statistically significant difference in the proportion of treatment completers between the olanzapine cohort (67.4%, 256/380) and the other SGA cohort (62.5%, 260/416). Treatment-completion rates were risperidone 62.0% (127/205), quetiapine 63.7% (123/193) and clozapine 55.6% (10/18). Antipsychotic polypharmacy was common. Patients treated with olanzapine or risperidone had significantly higher increases in BMI than quetiapine-treated patients. There were no major differences between olanzapine monotherapy and pooled other SGA monotherapy groups in status of extrapyramidal symptoms from baseline to endpoint. Conclusions: Olanzapine and other SGAs exhibited similar rates of 1-year treatment completion. Further study of medication combinations is needed, given their perceived clinical value, and the high frequency of antipsychotic polypharmacy in clinical practice. Limitations: As most patients received several psychotropics and power was reduced in monotherapy analyses, comparisons between cohorts must be interpreted cautiously. Comparisons between individual antipsychotics were post hoc and not powered a priori. Accuracy and completeness of adverse event information for drugs other than olanzapine is limited.