Cover: Prescribing of Clozapine and Antipsychotic Polypharmacy for Schizophrenia in a Large Medicaid Program

Prescribing of Clozapine and Antipsychotic Polypharmacy for Schizophrenia in a Large Medicaid Program

Published in: Psychiatric Services, [Epub February 2017]; doi:10.1176/

Posted on Mar 16, 2017

by Yan Tang, Marcela Horvitz-Lennon, Walid F. Gellad, Judith Lave, Chung-Chou H. Chang, Sharon-Lise T. Normand, Julie M. Donohue

Research Questions

  1. How does prescribing behavior for schizophrenia treatment vary among prescribers in the Pennsylvania Medicaid program?
  2. What factors are associated with this variation, and variation in patients' use?


Underuse of clozapine and overuse of antipsychotic polypharmacy are both indicators of poor quality of care. This study examined variation in prescribing clozapine and antipsychotic polypharmacy across providers, as well as factors associated with these practices.


Using 2010–2012 Pennsylvania Medicaid data, prescribers were identified if they wrote antipsychotic prescriptions for ten or more nonelderly adult patients with schizophrenia annually. Generalized linear mixed models with a binomial distribution and a logit link were used to examine prescriber-level annual percentages of patients with clozapine use and with long-term (≥90 days) antipsychotic polypharmacy and associated characteristics of prescribers’ patient caseloads, prescriber characteristics, and Medicaid payer (fee-for-service versus managed care plans).


The study cohort included 645 prescribers in 2010, 632 in 2011, and 650 in 2012. In 2012, the mean prescriber-level annual percentage of patients with any clozapine use was 7% (range 0%–89%), and the mean percentage of patients with any long-term antipsychotic polypharmacy was 7% (range 0%–45%) (similar rates were found during 2010–2012). Prescribers with high prescription volume, a smaller percentage of patients from racial or ethnic minority groups, and a larger percentage of patients eligible for Supplemental Security Income were more likely to use both clozapine and antipsychotic polypharmacy for treating schizophrenia. Prescriber specialty and Medicaid payer were also associated with prescribers’ practices.


Considerable variation was found in clozapine and antipsychotic polypharmacy practices across prescribers in their treatment of schizophrenia. Targeting efforts to selected prescribers holds promise as an approach to promote evidence-based antipsychotic prescribing.

Key Findings

  • The evidence base supports the use of clozapine for patients with treatment-resistant schizophrenia, but doctors in the study sample were as likely to prescribe nonclozapine antipsychotic medications, which are expensive and lack empirical support.
  • The rate of clozapine prescription in the sample signals likely underuse of the medication.
  • Evidence-based prescribing was not consistently associated with high volume of schizophrenia patients.
  • Doctors with the highest proportion of patients with schizophrenia-related hospitalization—an indicator to use clozapine—were more likely to follow recommended prescribing practices.
  • Variation in use of clozapine and nonclozapine antipsychotics across managed care plans suggests that plan formularies and utilization management practices may be playing a role in schizophrenia care quality.


State Medicaid programs, their managed care contractors, and other health care organizations could pursue strategies to improve evidence-based prescribing to treat schizophrenia, such as detailing and providing feedback to improve prescribers' knowledge, using financial incentives to reward intended behavior, and applying utilization management tools such as prior authorization and step therapy.

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