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Articles   |    
Geographic and Clinical Variation in Clozapine Use in the United States
T. Scott Stroup, M.D., M.P.H.; Tobias Gerhard, Ph.D.; Stephen Crystal, Ph.D.; Cecelia Huang, Ph.D.; Mark Olfson, M.D., M.P.H.
Psychiatric Services 2014; doi: 10.1176/appi.ps.201300180
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Dr. Stroup and Dr. Olfson are with the Department of Psychiatry, Columbia University College of Physicians and Surgeons, and the New York State Psychiatric Institute, New York City (e-mail: stroups@nyspi.columbia.edu). Dr. Crystal, Dr. Gerhard, and Dr. Huang are with the Institute for Health, Health Care Policy and Aging Research, Rutgers University, New Brunswick, New Jersey.

Copyright © 2014 by the American Psychiatric Association

Abstract

Objective  Antipsychotic medications are largely ineffective for approximately 30% of patients with schizophrenia that is considered “treatment resistant.” Clozapine is the only antipsychotic approved for treatment-resistant schizophrenia, but it is rarely used. This nationwide study examined predictors of clozapine use to help identify ways to optimize its use.

Methods  A retrospective study using U.S. Medicaid claims data from 45 states was conducted among 326,119 individuals with a schizophrenia spectrum disorder (ICD-9-CM code 295.X) who initiated one or more antipsychotic treatment episodes between January 2002 and December 2005. Multivariable logistic regression models were used to calculate odds ratios of baseline patient and county factors associated with clozapine initiation.

Results  Among 629,809 unique antipsychotic treatment episodes, 79,934 showed service use patterns consistent with treatment resistance. Clozapine accounted for 2.5% of starts of antipsychotic medication among patients in the overall sample and for 5.5% of starts among patients with treatment resistance. Clozapine initiation was significantly associated with male sex, younger age, white race, more frequent outpatient service use for schizophrenia, and greater prior-year hospital use for mental health. Treatment resistance and living in a county with historically high rates of clozapine use were among the strongest predictors of clozapine use.

Conclusions  The clozapine initiation rate was low compared with the expected proportion of patients who warrant a clozapine trial and was strongly affected by local treatment practices. Efforts to address irregular access to clozapine are needed to improve recovery opportunities for people with schizophrenia in the United States.

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Figure 1 Clozapine prescribing rates among Medicaid-insured adults with schizophrenia, January 2002–December 2005
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Table 1Characteristics of 629,809 treatment episodes of adult Medicaid beneficiaries with schizophrenia, by antipsychotic medication
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Table 2Adjusted odds of clozapine initiation among 629,809 antipsychotic episodes of adult Medicaid beneficiaries with schizophrenia, stratified by demographic and clinical characteristicsa
Table Footer Note

a Adjusted odds ratio (AOR) from a single logistic regression, with all variables entered as independent variables and antipsychotic medication (clozapine versus other) entered as the dependent variable. The analysis controlled for state, coded as individual dummy variables (state coefficients not shown).

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Table 3Likelihood of clozapine initiation among 629,809 antipsychotic episodes of adult Medicaid beneficiaries with schizophrenia, stratified by county characteristicsa
Table Footer Note

a Adjusted odds ratio (AOR) from a single logistic regression, with all variables in Tables 2 and 3 entered as independent variables and antipsychotic medication (clozapine versus other) entered as the dependent variable. The analysis controlled for state, coded as individual dummy variables (state coefficients not shown).

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