Response and Relapse in Patients With Schizophrenia Treated With Olanzapine, Risperidone, Quetiapine, or Haloperidol: 12-Month Follow-Up of the Intercontinental Schizophrenia Outpatient Health Outcomes (IC-SOHO) Study

Objective: The primary aim of this study was to compare the effectiveness of 12 months’ treatment with olanzapine, risperidone, quetiapine, or haloperidol in preventing relapse of schizophrenia. The study also examined other measures of clinical effectiveness and tolerability.

Method: Outpatients with schizophrenia (ICD-10 or DSM-IV), who initiated or changed antipsychotic treatment, entered this 3-year, naturalistic, prospective, observational study between November 2000 and December 2001. At baseline, subsets of patients were prescribed monotherapy with olanzapine (N = 3222), risperidone (N = 1116), quetiapine (N = 189), or haloperidol (N = 256). Patients remaining on monotherapy were assessed using the Clinical Global Impression-Schizophrenia scale. Relapse rate was determined from the responder subset. Treatment patterns, patient perception of treatment compliance, substance and alcohol intake patterns, and treatment tolerability were recorded. Results are based on 12-month treatment data.

Results: Compared to haloperidol-treated patients, olanzapine- and risperidone-treated patients had approximately 3 to 4 times higher odds of response at 12 months (p <= .001) and 6 times lower odds of relapse (p <= .001 for olanzapine-treated patients).Among patients treated with atypical antipsychotics, olanzapine- and risperidone-treated patients had lower odds of relapse (although the difference was not significant at p <= .001) and significantly higher odds of response (p <= .001) compared to quetiapine-treated patients. The tolerability profile generally favored the atypical antipsychotics over haloperidol.

Conclusion: These interim results support the findings of randomized controlled trials and verify that in this naturalistic study, patients treated with olanzapine or risperidone monotherapy were less likely to experience relapse than patients who received haloperidol. The clinical effectiveness and tolerability profile varied significantly between the atypical antipsychotics.