Patient, Physician and Organizational Influences on Variation in Antipsychotic Prescribing Behavior.

Background: Physicians face the choice of multiple ingredients when prescribing drugs in many therapeutic categories. For conditions with considerable patient heterogeneity in treatment response, customizing treatment to individual patient needs and preferences may improve outcomes.

Aims of the study: To assess variation in the diversity of antipsychotic prescribing for mental health conditions, a necessary although not sufficient condition for personalizing treatment. To identify patient caseload, physician, and organizational factors associated with the diversity of antipsychotic prescribing.

Methods: Using 2011 data from Pennsylvania's Medicaid program, IMS Health's HCOSTM database, and the AMA Masterfile, we identified 764 psychiatrists who prescribed antipsychotics to 10 patients. We constructed three physician-level measures of diversity/concentration of antipsychotic prescribing: number of ingredients prescribed, share of prescriptions for most preferred ingredient, and Herfindahl-Hirschman index (HHI). We used multiple membership linear mixed models to examine patient caseload, physician, and healthcare organizational predictors of physician concentration of antipsychotic prescribing.

Results: There was substantial variability in antipsychotic prescribing concentration among psychiatrists, with number of ingredients ranging from 2-17, share for most preferred ingredient from 16%-85%, and HHI from 1,088-7,270. On average, psychiatrist prescribing behavior was relatively diversified; however, 11% of psychiatrists wrote an average of 55% of their prescriptions for their most preferred ingredient. Female prescribers and those with smaller shares of disabled or serious mental illness patients had more concentrated prescribing behavior on average.

Discussion: Antipsychotic prescribing by individual psychiatrists in a large state Medicaid program varied substantially across psychiatrists. Our findings illustrate the importance of understanding physicians' prescribing behavior and indicate that even among specialties regularly prescribing a therapeutic category, some physicians rely heavily on a small number of agents.

Implications for health policies, health care provision and use: Health systems may need to offer educational interventions to clinicians in order to improve their ability to tailor treatment decisions to the needs of individual patients.

Implications for future research: Future studies should examine the impact of the diversity of antipsychotic prescribing to determine whether more diversified prescribing improves patient adherence and outcomes.