Differences in Treatment Effect Among Clinical Subgroups in a Randomized Clinical Trial of Long-Acting Injectable Risperidone and Oral Antipsychotics in Unstable Chronic Schizophrenia

Abstract

A long-term randomized trial of unstable patients with schizophrenia found no benefit of long-acting injectable (LAI) risperidone over oral treatment in preventing or delaying time to psychiatric hospitalizations or on clinical outcomes. The initial analyses did not examine whether benefits of LAI emerged in selected subgroups.Patients with schizophrenia or schizoaffective disorder who had been hospitalized within the past 2 years or judged to be at risk for hospitalization because of increasing psychiatric service use were randomly assigned to LAI risperidone 12.5 to 50 mg per injection biweekly or to the psychiatrist's choice of oral antipsychotics and followed for up to 2 years. The primary endpoint was psychiatric rehospitalization. Symptoms, quality of life, and global functioning were assessed through blinded videoconference interviews. Cox's regression and mixed effects models were used to assess difference in treatment effect within 12 subgroups defined by hospitalization at study entry, substance abuse, race, symptom severity, quality of life, body mass index, age, race or sex, or reported medication compliance.Mixed models and Cox's regression using up to 24 months of follow-up data showed no significant differences in treatment effect in 10 of 12 subgroups on psychiatric symptoms, quality of life, or time to hospitalization. With adjustment for multiple comparisons, treatment effect differed by race on substance use outcomes, with white participants showing more benefit from LAI than other groups.LAI risperidone showed no superiority to psychiatrist's choice of oral treatment in most clinically defined subgroups, although the white patients benefited more than the other groups on substance abuse outcomes.