The Safety of Olanzapine Compared With Other Antipsychotic Drugs: Results of an Observational Prospective Study in Patients With Schizophrenia (EFESO Study)

Introduction: Results of controlled clinical trials should be confirmed through safety and effectiveness studies in nonselected patient cohorts treated according to routine clinical practice.

Method: Outpatients with schizophrenia (ICD-10 criteria) entered this prospective, naturalistic study when they received a new prescription for an antipsychotic drug. Treatment assignment was based on purely clinical criteria, as the study did not include any experimental intervention. Safety was evaluated through the collection of spontaneous adverse events and a specific questionnaire for extrapyramidal symptoms. Global clinical status was measured through the Clinical Global Impressions-Severity (CGI-S) and the Global Assessment of Functioning (GAF) scales.

Results: From the 2967 patients included, 2128 patients were treated with olanzapine as monotherapy or combined with other drugs (olanzapine group), and 821 were treated with other antipsychotic drugs as monotherapy or combined with other drugs (control group). There were no statistical differences between treatment groups at baseline regarding age, gender, disease duration, or severity of symptoms. Olanzapine was well tolerated and effective in this study. Overall incidence of adverse events was significantly lower in the olanzapine group compared with the control group (p < .001). Somnolence and weight gain were significantly more frequent in the olanzapine group, and akathisia, dystonia, extrapyramidal syndrome, hypertonia, hypokinesia, and tremor were significantly higher in the control group. Clinical improvement at endpoint, measured through the mean change in the CGI-S and the GAF, was significantly higher in the olanzapine group compared with the control group (p = .004).

Conclusion: These results show that olanzapine is safe and effective in nonselected schizophrenic outpatients and are consistent with the efficacy and safety profile that olanzapine has shown in previous controlled clinical trials.