Antipsychotic polypharmacy vs. monotherapy in the treatment of schizophrenia
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Antipsychotic polypharmacy or concomitant use of multiple antipsychotics is prevalent in up to 40% of schizophrenia patients despite lack of clinical evidence or support from treatment guidelines. The objective of this study was to estimate the prevalence and trends of antipsychotic polypharmacy, identify patient factors associated with its use and determine its effect on health care cost and community tenure. Medicaid recipients >=16 years of age with at least one primary diagnosis of schizophrenia (ICD-9-CM=295.**) between 1998-2000 were identified from the Georgia and California (20% random sample) Medicaid claims databases. Antipsychotic polypharmacy cohorts were built in a hierarchical fashion based on antipsychotic use profile i.e. any antipsychotic polypharmacy, clozapine (clozapine + atypical; clozapine + conventional), non-clozapine (atypical+atypical; conventional+conventional; and atypical+conventional) and long-term i.e. duration of use > 2 months and compared with monotherapy controls. 3-year prevalence rates, year wise trends, per capita net oneyear expenditure and one-year hazard rates for hospitalization were reported after adjusting for selection bias. Out of a total of 31,435 persons with schizophrenia, the overall prevalence of antipsychotic polypharmacy was 40% (n=12,549, mean age: 43 years, white: 47%, female: 48%) over 1998-2000 and prevalence of atypical polypharmacy had increased between 1998 and 2000. Long-term antipsychotic polypharmacy had a prevalence rate of 23% (n=7,222) with a long-term episode lasting a median of 197 days. The one-year per capita expenditure for the long-term antipsychotic polypharmacy group was $13,891 which was significantly higher ($3,829 95% Confidence Interval [CI], 3,347 to 4,310) than the monotherapy group ($10,062) and remained higher even after adjustment for selection bias ($1,699 95% CI 760 to 2,638). Polypharmacy was associated with a higher one-year (1.25, 95% CI 1.09 TO 1.41) and two-year (1.45, 95% CI 1.27 to 1.63) hospitalization risk. We did not find any evidence of economic and hospitalization risk related benefit with antipsychotic polypharmacy except a significant net cost in the clozapine+conventional vs clozapine sensitivity analysis (p < 0.0001). Our findings raise concerns regarding the value of antipsychotic polypharmacy and emphasize the need to critically evaluate such treatment decisions in schizophrenia patients.