Purpose: Patterns of pharmacologic treatment in U.S. outpatients with schizophrenia across multiple health care settings were investigated.
Methods: Antipsychotic drug utilization by patients with schizophrenia and related disorders was analyzed using data on 119,662 patients served by the Veterans Affairs (VA) health care system in fiscal years 2005-09, data on 5,440 enrollees in two health maintenance organizations (HMOs) in 2002-09, and National Ambulatory Medical Care Survey (NAMCS) data reflecting the experience of 17.6 million U.S. residents seeking care outside federal systems during the same eight-year period. Polypharmacy was defined as the use of more than one antipsychotic agent during one year (in the VA sample) or one week (in the HMO and NAMCS samples). The association of polypharmacy with hospital admissions was assessed via multivariable logistic regression.
Results: Rates of antipsychotic use in the VA sample ranged from 74% to 78%, with lower and more variable rates in the NAMCS sample (69-84%) and the HMO sample (22-67%). VA patients were found to have lower polypharmacy rates (20-22%) than patients in the HMO and NAMCS samples (19-31%). In all samples evaluated, polypharmacy was associated with an increased likelihood of hospital admission (odds ratio range, 1.4-2.4).
Conclusion: A multisystem study revealed that antipsychotic use among patients with schizophrenia varied substantially among health care systems and that nearly one fifth of patients with schizophrenia or other psychotic disorders in most of the health care systems experienced antipsychotic polypharmacy.