Prevalence, trends, and factors associated with antipsychotic polypharmacy among Medicaid-eligible schizophrenia patients, 1998-2000.

Objective: To determine the prevalence, trends, and factors associated with antipsychotic polypharmacy categorized according to type of antipsychotic and duration of use and to contrast usage patterns with published treatment guidelines. Method: A retrospective cohort study was designed, and Medicaid recipients ≥ 16 years of age with a schizophrenia diagnosis (ICD-9-CM = 295.xx) between 1998 and 2000 were identified from the California (20% random sample) and Georgia Medicaid claims databases. Use of antipsychotic polypharmacy was categorized based on duration (long-term polypharmacy was defined as lasting > 2 months), and long-term use was further categorized based on type of antipsychotic combinations (clozapine, conventional, and atypical). The prevalence, mean duration, and frequency of and yearwise trends in antipsychotic polypharmacy were estimated. A stepwise logistic variable selection procedure was used to identify factors associated with long-term antipsychotic polypharmacy. Results: Of a total of 31,435 persons with schizophrenia, the 1998-2000 prevalence of antipsychotic polypharmacy was 40% (N = 12,549; mean age = 43 years; white, 47%; female, 48%; mean duration of polypharmacy = 149 days), and long-term antipsychotic polypharmacy prevalence was 23% (N = 7222, mean duration = 236 days). The prevalence of atypical antipsychotic polypharmacy increased between 1998 and 2000 (p <.0001). Use of newer atypicals such as quetiapine (OR = 18.32) and older conventionals such as chlorpromazine (OR = 28.87) was strongly associated with long-term antipsychotic polypharmacy. Conclusion: Antipsychotic polypharmacy is widely prevalent, is prescribed for long durations, and is an increasing phenomenon among Medicaid-eligible schizophrenia patients, indicating a significant discrepancy with treatment guidelines (which do not advocate the use of any polypharmacy except for short-term periods when transitioning patients to new antipsychotics). Further research evaluating the effects of antipsychotic polypharmacy in schizophrenia patients may assist in defining the scope and potential of such use.