National Prescribing Trends of Metformin Before and After the 2022 Treatment Guideline Update

Abstract

Purpose: Prior to 2022, metformin was referenced as the first-line treatment option for Type 2 Diabetes Mellitus (T2DM) per the American Diabetes Association (ADA) Standards of Care in Diabetes guidelines. Since 2022, first-line treatment for T2DM is now centered around patient-specific factors like comorbidities, cost, and access considerations. The objective of this study was to compare the prescribing trends of metformin before and after the first-line therapy recommendations for T2DM management nationwide.

Methods: This was an evaluative study conducted using a retrospective analysis on the Centers of Medicare and Medicaid Services public database from 2021 to 2023, which provided information on the prescribing rates nationwide. Data was aggregated by filtering each state’s total number of metformin claims and total beneficiaries who received Medicare or Medicaid services that year. All brand and generic formulations of monotherapy metformin were included. Territories and regions outside of the United States and combination medications with metformin were excluded. The estimated prescribing rates for each state were calculated by dividing the total number of metformin claims by the beneficiaries per 1000 for all medications. Then, the differences in estimated prescribing rates per state were calculated and extrapolated to a US heat map for further analysis.

Results: Prior to the ADA guideline update, the top three states with the highest claims in 2021 were North Dakota (90), California (82), and Nebraska (81). With the first-line recommendation update in the ADA 2022 guidelines, the top three highest claims were in North Dakota (90), California (80), and Nebraska (79). In 2023, the top three states were North Dakota (85), California (77), and Minnesota (75). Overall, California and North Dakota continued to have the highest total number of metformin claims across all 3 years. Additionally, all states had a downward trend in prescribing rates of metformin from 2021 to 2023 with a difference ranging from -3 to -9. The states with the highest difference (-9) were Alaska and Iowa.

Conclusion: Overall, a general downward trend in the prescribing rates indicated that metformin use has been gradually decreasing after the 2022 ADA guideline update. It should be noted that there was already a downtrend in prescribing rates before the guideline update. A limitation of this study was the lack of available data since the 2022 guideline update and the exclusion of combination therapies. Future research could assess combination therapies and extend the observation period beyond 2023.