Introduction: This article presents the long-term results in terms of antipsychotic medication maintenance and factors influencing it in a representative sample of patients with schizophrenia recruited in the SOHO study within Spain.
Methods: The SOHO was a prospective, 3-year observational study of the outcomes of schizophrenia treatment in outpatients who initiated therapy or changed to a new antipsychotic performed in 10 European countries with a focus on olanzapine. The Kaplan-Meier method was used to analyse the time to treatment discontinuation and the Cox proportional hazards model to investigate correlates of discontinuation.
Results and conclusions: In total, 1688 patients were included in the analyses. Medication maintenance at 3years varied with the antipsychotic prescribed, being highest with clozapine (57.6%, 95% CI 39.2-74.5), followed by olanzapine (48.3%, 95% CI 45.1-51.5); and lowest with quetiapine (19.0%, 95% CI 13.0-26.3). Treatment discontinuation was significantly less frequent with olanzapine than with risperidone (p=0.015), depot typical (p=0.001), oral typical antipsychotics (p<0.001) or quetiapine (p<0.001); but not than with clozapine (p=0.309). Longer maintenance was also associated with higher social abilities and better cognitive status at baseline; in contrast, a shorter time to discontinuation was associated with the need for mood stabilisers during follow-up. This study emphasises the different value of antipsychotics in day-to-day clinical practice, as some of them were associated with longer medication maintenance periods than others. This study has some limitations because of possible selection and information biases derived from the non-systematic, non-randomised allocation to treatments and the existence of unobserved covariates that may influence the outcome.