Medication adherence and utilization in patients with schizophrenia or bipolar disorder receiving aripiprazole, quetiapine, or ziprasidone at hospital discharge: A retrospective cohort study

BACKGROUND Schizophrenia and bipolar disorder are chronic debilitating disorders that are often treated with second-generation antipsychotic agents, such as aripiprazole, quetiapine, and ziprasidone. While patients who are hospitalized for schizophrenia and bipolar disorder often receive these agents at discharge, comparatively little information exists on subsequent patterns of pharmacotherapy. METHODS Using a database linking hospital admission records to health insurance claims, we identified all patients hospitalized for schizophrenia (ICD-9-CM diagnosis code 295.XX) or bipolar disorder (296.0, 296.1, 296.4-296.89) between January 1, 2001 and September 30, 2008 who received aripiprazole, quetiapine, or ziprasidone at discharge. Patients not continuously enrolled for 6 months before and after hospitalization ("pre-admission" and "follow-up", respectively) were excluded. We examined patterns of use of these agents during follow-up, including adherence with treatment (using medication possession ratios [MPRs] and cumulative medication gaps [CMGs]) and therapy switching. Analyses were undertaken separately for patients with schizophrenia and bipolar disorder, respectively. RESULTS We identified a total of 43 patients with schizophrenia, and 84 patients with bipolar disorder. During the 6-month period following hospitalization, patients with schizophrenia received an average of 101 therapy-days with the second-generation antipsychotic agent prescribed at discharge; for patients with bipolar disorder, the corresponding value was 68 therapy-days. Mean MPR at 6 months was 55.1% for schizophrenia patients, and 37.3% for those with bipolar disorder; approximately one-quarter of patients switched to another agent over this period. CONCLUSIONS Medication compliance is poor in patients with schizophrenia or bipolar disorder who initiate treatment with aripiprazole, quetiapine, or ziprasidone at hospital discharge.