Variation of Clozapine Use for Treatment of Schizophrenia: Evidence from Pennsylvania Medicaid and Dually Eligible Enrollees.

While clozapine is the most effective antipsychotic treatment for treatment-resistant schizophrenia, it remains underutilized across the United States, warranting a more comprehensive understanding of variation in use at the county level, as well as characterization of existing prescribing patterns. Here, we examined both Medicaid and Medicare databases to (1) characterize temporal and geographic variation in clozapine prescribing and, (2) identify patient-level characteristics associated with clozapine use. We included Medicaid and Fee for Service Medicare data in the state of Pennsylvania from January 1, 2013, through December 31, 2019. We focused on individuals with continuous enrollment, schizophrenia diagnosis, and multiple antipsychotic trials. Geographic variation was examined across counties of Pennsylvania. Regression models were constructed to determine demographic and clinical characteristics associated with clozapine use. Out of 8,255 individuals who may benefit from clozapine, 642 received treatment. We observed high medication burden, overall, including multiple antipsychotic trials. We also identified variation in clozapine use across regions in Pennsylvania with a disproportionate number of prescribers in urban areas and several counties with no identified clozapine prescribers. Finally, demographic, and clinical determinants of clozapine use were observed including less use in people identified as non-Hispanic Black, Hispanic, or with a substance use disorder. In addition, greater medical comorbidity was associated with increased clozapine use. Our work leveraged both Medicaid and Medicare data to characterize and surveil clozapine prescribing. Our findings support efforts monitor disparities and opportunities for the optimization of clozapine within municipalities to enhance clinical outcomes.