Objective: To compare second-generation antipsychotics on time to and cost of psychiatric hospitalization in Medicaid beneficiaries with bipolar disorder.
Methods: Retrospective study using healthcare claims from 10 US state Medicaid programs. Included beneficiaries were aged 18-64, initiated a single second-generation antipsychotic (aripiprazole, olanzapine, quetiapine, risperidone, or ziprasidone) between 1/1/2003-6/30/2008 (initiation date=index), and had a medical claim with an ICD-9-CM diagnosis code for bipolar disorder. A 360-day post-index period was used to measure time to and costs of psychiatric hospitalization (inpatient claims with a diagnosis code for a mental disorder [ICD-9-CM 290.xx-319.xx] in any position). Cox proportional hazards models and Generalized Linear Models compared time to and costs of psychiatric hospitalization, respectively, in beneficiaries initiating aripiprazole vs each other second-generation antipsychotic, adjusting for beneficiaries' baseline characteristics.
Results: Included beneficiary characteristics: mean age 36 years, 77% female, 80% Caucasian, aripiprazole (n=2553), mean time to psychiatric hospitalization or censoring=85 days; olanzapine (n=4702), 81 days; quetiapine (n=9327), 97 days; risperidone (n=4377), 85 days; ziprasidone (n=1520), 82 days. After adjusting for baseline characteristics, time to psychiatric hospitalization in beneficiaries initiating aripiprazole was longer compared to olanzapine (hazard ratio [HR]=1.52, p<0.001), quetiapine (HR=1.40, p<0.001), ziprasidone (HR=1.33, p=0.032), and risperidone, although the latter difference did not reach significance (HR=1.18, p=0.13). The adjusted costs of psychiatric hospitalization in beneficiaries initiating aripiprazole were significantly lower compared to those initiating quetiapine (incremental per-patient per-month difference=$42, 95% CI=$16-66, p<0.05), but not significantly lower for the other comparisons.
Limitations: This study was based on a non-probability convenience sample of the Medicaid population. Analyses of administrative claims data are subject to coding and classification error.
Conclusions: Medicaid beneficiaries with bipolar disorder initiating aripiprazole had significantly longer time to psychiatric hospitalization than those initiating olanzapine, quetiapine, or ziprasidone, and significantly lower adjusted costs for psychiatric hospitalization than those initiating quetiapine.