Cost analysis in a Medicaid program for patients with bipolar disorder who initiated atypical antipsychotic monotherapy

ABSTRACTBackground: Use of atypical antipsychotics in treatment of patients with bipolar disorder is increasingly common, yet few studies have systematically investigated or compared medical costs associated with use of specific atypical antipsychotics.Objective: To evaluate the direct healthcare costs associated with olanzapine, risperidone, or quetiapine monotherapy among Medicaid patients diagnosed with bipolar disorder (ICD-9: 296.4x-296.8x).Methods: North Carolina Medicaid patients with bipolar disorder were followed for 12 months after initiation of atypical antipsychotic monotherapy (index date). They had no bipolar-related medical visit, hospitalization, or use of atypical antipsychotics 90-days prior to the treatment initiation. Costs of index drug, all bipolar-related medical care, and all health-related costs were examined. A two-stage sample selection model was employed to account for potential confounders and sample selection bias. Medication adherence measures using cumulative medication acq...