OBJECTIVE: This analysis assessed rates of medication adherence and predictors of nonadherence and hospitalization among patients treated with long-acting injectable and oral antipsychotic therapies.
METHODS: Data were from a retrospective analysis of Florida Medicaid recipients with schizophrenic disorder (ICD-9-CM code 295.XX) who received a prescription for an antipsychotic between July 1, 2004, and June 30, 2005. Patients were required to have filled one additional antipsychotic prescription during follow-up. Adherence measures included medication possession ratio (MPR), medication persistence, medication consistency, and maximum gap in treatment. Multivariate logistic regression models identified predictors of nonadherence and hospitalization.
RESULTS: Patients were considered adherent if they had an MPR ≥.8. A total of 12,032 patients met selection criteria. The mean±SD MPR was .79±.23, medication persistence was 94.1%±16.4%, medication consistency was 83.3%±16.4%, and the maximum gap in treatment was 29.7±41.4 days. Thirty-seven percent of patients were hospitalized for any cause, and 32% had a psychiatric hospitalization. Predictors of nonadherence included newly starting treatment; younger age; a substance abuse diagnosis; use of a mood stabilizer, antidepressant, anxiolytic, or anticholinergic; and receipt of long-acting first-generation antipsychotics. Receipt of long-acting second-generation therapy or receipt of both first- and second-generation medications was associated with lower likelihood of nonadherence. Predictors of hospitalization risk included a diagnosis of other psychoses or substance abuse, anticholinergic use, and nonadherence to therapy.
CONCLUSIONS: Results document rates of antipsychotic adherence and predictors of nonadherence and hospitalization. Findings may be useful to health plan administrators, formulary decision makers, and physicians.
