Thirteen-fold variation between states in clozapine prescriptions to United States Medicaid patients

Background Clozapine was the first atypical antipsychotic for treating schizophrenia, with a long history of controversy over its usage. Guidelines currently recommend clozapine for patients diagnosed with refractory schizophrenia. However, this agent may be underutilized because of the costs associated with close monitoring of its adverse effects, particularly agranulocytosis. This is unfortunate because clozapine has demonstrated greater effectiveness compared with other antipsychotics. It is essential to examine clozapine usage to determine if it is being adequately utilized among United States (US) Medicaid patients. Methods Medicaid data, including the number of quarterly clozapine prescriptions and the number of Medicaid enrollees in each state from 2015-2019, was collected and used to evaluate clozapine use over time. Data-analysis and figures were prepared with Excel and GraphPad Prism. Exploratory correlations were completed between prescriptions per enrollee and other factors. Results The number of prescriptions, corrected for the number of enrollees in Medicaid, was generally consistent over time. However, average prescriptions per quarter were markedly lower in 2017 compared with other years, decreasing by 44.4% from 2016 average prescriptions per quarter. From 2015 to 2019, states from the upper Midwest and Northeast regions of the country had the highest average clozapine prescriptions per 10,000 Medicaid enrollees (ND: 190.0, SD: 176.6, CT: 166.2). States from the Southeast and Southwest had much lower average rates (NV: 17.9, KY: 19.3, MS: 19.7). There was an over ten-fold difference in clozapine prescriptions between states from 2015-2019 (2015 = 19.9-fold, 2016=11.4 fold, 2017=11.6 fold, 2018=13.3 fold, and 2019=13.0 fold). There was a moderate correlation of (r(48) = 0.49, p < .05) between prescriptions per 10,000 enrollees and the Medicaid spending per enrollee in each state in 2019. There was a small, but significant, correlation between prescriptions per enrollee and percent white (r(48) = 0.30, p < .05). Conclusion Clozapine is an important pharmacotherapy for refractory schizophrenia. Overall, clozapine use tends to be highest among the upper Midwest and Northeast states. Further research is ongoing to better understand the origins of the thirteen-fold regional disparities in clozapine use in 2019 and the state level variation in Medicaid spending.