Pmh33: Olanzapine Versus Risperidone in the Treatment of Schizophrenia: A Comparison of Costs Among Texas Medicaid Patients

Abstract

OBJECTIVE: The purpose of this retrospective study is to examine both schizophrenia‐related direct costs and total (schizophrenia plus non‐schizophrenia) direct costs among Texas Medicaid patients who have been diagnosed with a schizophrenic disorder and have been initiated on one of two atypical antipsychotics (olanzapine or risperidone). METHODS: Services and prescription utilization and cost data were retrieved for 3,072 patients with schizophrenia who were initiated on olanzapine or risperidone between 1997 and 1998. Each patient was followed for one year from initiation of therapy. Multivariate analysis was used to control for a wide range of factors (drug choice, patient demographics, pre‐utilization costs, region, health conditions, and treatment patterns) that may influence schizophrenia‐related costs and total costs. Estimation was conducted via a two‐stage instrumental variable model. RESULTS: The mean unadjusted total schizophrenia‐related cost per patient per year was $4,973, and the total unadjusted health care cost per patient per year was $7,335. Although the daily drug costs associated with olanzapine were higher than risperidone, and patients taking olanzapine on average stayed on therapy longer than those taking risperidone, when looking at total schizophrenia‐related costs (services plus prescription utilization), there was no significant difference between drug groups (olanzapine $81 lower, p = 0.7534). Additionally, when total health care costs were analyzed, there was no significant difference in drug groups (olanzapine $530 lower, p = 0.1050). Sensitivity analyses found similar results. CONCLUSION: This naturalistic study used data from a Texas Medicaid population to examine the schizophrenia‐related costs (and total costs) for patients who received olanzapine versus risperidone. No differences in direct costs were found for patients receiving olanzapine versus risperidone.

Identifying Patient Characteristics Associated with High Schizophrenia-Related Direct Medical Costs in Community-Dwelling Patients

“…15 Although our study included home health care costs and inpatient costs, it did not include nursing home costs, which could explain the negative relationship found between age and costs. A similar negative relationship between age and schizophrenia-related costs was also observed by Rascati et al (2003). 17 Patients with a spouse or those under age 16 had significantly lower schizophrenia-related expenditures compared with those without a spouse.…”

“…[14][15][16][17] The prevalence of schizophrenia varies by age, gender, race, insurance status, family income as a percentage of poverty line, and marital status. 3,18 Thus, we also expected the costs to vary by these factors.…”

Characteristics of Outpatients Initiated on Olanzapine versus Risperidone in the Treatment of Schizophrenia in Japan: A Healthcare Database Analysis

“…In the United States, olanzapine initiators were found to have more complex psychiatric histories than risperidone initiators including more pre-existing psychiatric comorbidities [20], more prior use of other classes of psychiatric medications [20,21], higher prior psychiatric inpatient costs [22], more previous treatment with clozapine [21,23,24], and more initial prescriptions from psychiatrists [24]. Consistent with these prior studies, olanzapine initiators in the current analysis were more likely to have diagnoses for manic episodes and had more prior antidepressant use.…”

“…Consistent with these prior studies, olanzapine initiators in the current analysis were more likely to have diagnoses for manic episodes and had more prior antidepressant use. In the United States, risperidone was found to be initiated more often than olanzapine for patients with schizophrenia who have more physical comorbidities [20,[22][23][24][25]. Consistent with these studies, the univariate analysis found that risperidone initiators were more likely to have previous claims for diabetes mellitus.…”

Instrumental Variable Analysis in Epidemiologic Studies: An Overview of the Estimation Methods

“…There is a rule of thumb that if the F-statistic value is greater than 10, the first assumption holds [13,96,97]. Other measures for the strength of the association between IVand exposure include the first-stage regression coefficient of the IV [50,98] or the R 2 of a linear first-stage model [15,78,83], the odds ratio [6,93], or pseudo-R-squared of the first-stage model [76]. When the correlation between IVand exposure is not strong enough, IVanalysis is likely to be biased (weak IV bias, which increases with the weakness of the IV).…”