OBJECTIVES: In 2021, approximately 10 percent of adults in California had diabetes, and 80 percent of those diagnosed took medication to manage their condition. The purpose of this study is to evaluate the clinical effectiveness of Metformin-based therapies for Medicare and Medi-Cal diabetes patients.

METHODS: This study examined the 2034 Medicare and 11747 Medi-Cal diabetes patients in the Inland Empire in 2022. The clinical outcomes evaluated were the Healthcare Effectiveness Data and Information Set (HEDIS) quality measure Hemoglobin A1c Control for Patients with Diabetes (HbA1c<8.0%) and emergency visits. We assessed three Metformin-based combination therapies, in reference to Metformin monotherapy: Metformin + Glipizide, Metformin + Glucagon-Like Peptide-1 Receptor (GLP-1) Agonists, and Metformin + Sodium-Glucose Cotransporter-2 (SGLT2) Inhibitors. Prescription patterns and HbA1c control rates were analyzed through propensity score estimation and weighting.

RESULTS: Medicare and Medi-Cal patients on the three combination therapies have significantly lower odds of achieving HbA1c control, with Metformin + Glipizide being the least effective, in comparison to Metformin monotherapy. No significant difference in emergency visits was detected. Patients with medication adherence had 54% (p=0.029) increase in odds of attaining HbA1c control in Medicare cohort and 68% (p<0.001) in Medi-Cal cohort. Metformin + SGLT2 Inhibitors was 73% (p=0.022) more likely to be prescribed to Medicare patients and 210% (p<0.001) to Medi-Cal patients. Having at least one PCP-visit in the year corresponded to a 421% (p<0.001) increase in likelihood of obtaining HbA1c control in Medi-Cal cohort.

CONCLUSIONS: This study demonstrates cardiovascular benefits of Metformin + SGLT2 Inhibitors, for the cohort on this treatment, which contains higher percentage of heart-failure patients, shows no significant increase in cardiovascular-related emergency visit. In terms of HbA1c control, Metformin monotherapy is the most cost-effective option, while Metformin + Glipizide prescription needs to be reconsidered due to poor performance. Additionally, medication adherence and PCP visit have significant positive impact.