Efficacy of olanzapine and risperidone in schizophrenia: a randomized double-blind crossover design

Abstract

This article compares the efficacy of olanzapine and risperidone for positive and negative symptoms using an 18-week, randomized, double-blind, crossover design. The hypotheses were that olanzapine would be more efficacious for treating negative symptoms, and that risperidone would be superior in treating positive symptoms. Positive and negative symptoms scores improved throughout treatment, regardless of medication type. Differences between the medications were found for negative and general psychopathology rating scales. Overall, olanzapine led to greater improvements in negative symptoms than did risperidone. When each scale was analyzed individually, greater improvements were found for olanzapine on Positive and Negative Symptoms Scale (PANSS) General,PANSS total, and Scale for the Assessment of Negative Symptoms (SANS)attention. A nearly significant trend favoring olanzapine was found for the Calgary Depression Scale. Several negative symptom subscales followed a nonsignificant trend toward olanzapine being more efficacious than risperidone.Thus, there was a very consistent pattern of greater efficacy for olanzapine, particularly for negative symptoms. Despite the small number of subjects, this study shows the potential of a within-subject design to elucidate differences in efficacy.