Olanzapine versus risperidone in the treatment of schizophrenia : a comparison of costs among Texas Medicaid recipients.

OBJECTIVE: To examine both schizophrenia-related costs and total (schizophrenia plus non-schizophrenia) healthcare costs among Texas Medicaid recipients who had been diagnosed with a schizophrenic disorder and had been initiated on olanzapine or risperidone.
METHODS: Cost data for services and prescription use were retrieved for 2,885 patients with schizophrenia who were initiated on olanzapine or risperidone between 1 January 1997 and 31 August 1998. Each patient was followed for 1 year before and 1 year after initiation of therapy. Multivariate analysis was used to control for a wide range of factors (drug choice, patient demographics, pre-utilisation costs, region, health conditions, and treatment patterns) that may influence schizophrenia-related costs and total healthcare costs. Estimation was conducted via a two-stage instrumental variables model.
RESULTS: The mean unadjusted total schizophrenia-related cost per patient per year during the observation period was 4,892 US dollars, and the total unadjusted healthcare cost per patient was 7,101 US dollars. Results revealed significant regional variation in schizophrenia-related and total healthcare costs. Significantly higher total healthcare costs were found for patients with other (nonpsychiatric) diagnoses, such as HIV and diabetes mellitus. Although, on average, patients taking olanzapine stayed on therapy longer than those taking risperidone (248.2 days vs 211.1 days; p < 0.0001), multivariate analysis revealed no significant difference in schizophrenia-related costs between patients who received olanzapine and risperidone (123 US dollars lower with olanzapine; p = 0.6439). However, patients who received olanzapine compared with risperidone had significantly lower total medical costs (693 US dollars lower with olanzapine; p = 0.0311).
CONCLUSION: This naturalistic study used data from a Texas Medicaid population to examine the schizophrenia-related costs and total healthcare costs for patients who received olanzapine versus risperidone. Multivariate analysis revealed no significant differences in schizophrenia-related costs for patients receiving olanzapine compared with risperidone, although total medical costs were significantly lower for patients initiated on olanzapine.