Olanzapine versus risperidone. A prospective comparison of clinical and economic outcomes in schizophrenia

Abstract

Objective: To compare the clinical and economic outcomes associated with olanzapine and risperidone treatment for schizophrenia.

Design and setting: An international, multicentre, double-blind, prospective study. To facilitate economic comparisons, our sample was restricted to patients enrolled in US sites. 150 patients with a Diagnostic and Statistical Manual of mental disorders, 4th edition (DSM-IV) diagnosis of schizophrenia, schizoaffective disorder or schizophreniform disorder were randomised to therapy with either olanzapine 10 to 20 mg/day (n = 75) or risperidone 4 to 12 mg/day (n = 75) for a maximum of 28 weeks. In addition to tolerability and efficacy assessments, use of health services was assessed at baseline and prospectively, at 8-week intervals and at study completion. Clinically important response, defined as a 40% improvement in the Positive and Negative Syndrome Scale total score, maintenance of response and rates of treatment-emergent extrapyramidal symptoms were compared between groups. Direct medical costs were estimated by assigning standardised prices to resource units. Median total, inpatient/outpatient service and medication acquisition costs were compared between treatment groups.

Main outcome measures and results: The mean modal dosages for the olanzapine and risperidone treatment groups were 17.7 +/- 3.4 mg/day and 7.9 +/- 3.2 mg/day, respectively. Olanzapine-treated patients were more likely to maintain response compared with risperidone-treated patients (p = 0.048). In addition, a smaller proportion of olanzapine-treated patients required anticholinergic therapy compared with risperidone-treated patients (25.3 vs 45.3%; p = 0.016). Total per patient medical costs over the study interval were $US2843 (1997 values) [36%] lower in the olanzapine treatment group than in the risperidone treatment group (p = 0.342). Medication costs were significantly higher for olanzapine-treated patients ($US2513 vs $US1581; p < 0.001), but this difference was offset by a reduction of $US3774 (52%) in inpatient/outpatient service costs for olanzapine-treated patients in comparison with risperidone-treated patients ($US3516 vs $US7291, p = 0.083). Median cost findings were consistent with results observed using other robust measures of central tendency and provide conservative estimates of potential savings that may be obtained from olanzapine therapy.

Conclusions: In this study, olanzapine-treated patients experienced clinical improvements that translated into savings in costs of care for both inpatient and outpatient services. These savings offset the difference in medication acquisition cost between olanzapine and risperidone.