Abstract 037: The U.S. Food and Drug Administration’s Metformin Label Change Reduces Racial Disparity in Metformin Use by Increasing Its Use Among Black Patients With Type 2 Diabetes and Moderately Impaired Kidney Function

Abstract

Introduction: Historically, metformin was contraindicated in people with type 2 diabetes (T2D) and kidney disease due to concerns of lactic acidosis. The U.S. Food and Drug Administration (FDA) recently changed metformin label from serum creatinine (sCr)-based to estimated glomerular filtration (eGFR)-based indication, expanding its use for people with eGFR≥30 mL/min/1.73 m 2 . The purpose of our study is to assess the effects of the label change on metformin use among people with T2D, stratified by race and eGFR. Hypothesis: Because sCr levels are higher in blacks than in whites at the same level of eGFR, we hypothesized that the label change increases metformin use in people with T2D and kidney disease and magnitude of increase is greater in blacks than in whites. Methods: One-year period prevalence cohort was created for each of before and after the FDA’s label change (April 8, 2016) in Johns Hopkins Medicine, including people with T2D and eGFR≥30 mL/min/1.73 m 2 . We estimated the prevalence of metformin use in each cohort, stratified by eGFR within each race. Results: Mean age of study population (N=15,880) was 61 years, 52% were women, 48% were black, mean eGFR was 81 mL/min/1.73 m 2 , and mean HbA1c was 7.8%. Before the label change, blacks with eGFR 30-44 mL/min/1.73 m 2 were less likely to use metformin compared to whites, controlling for age, sex, eGFR, and HbA1c (odds ratio [OR]=0.49 [95% confidence interval: 0.37-0.65]). The label change did not increase metformin use among whites across all categories of eGFR, whereas it increased metformin use from 26.1% to 32.6% (P=0.03) among blacks with eGFR 30-44 ml/min/1.73 m 2 ( Figure ). As a result, magnitude of racial disparity in metformin use after the label change was attenuated (OR=0.75 [0.57-0.99]). Conclusions: The recent eGFR-based metformin label change increased its use in black people with T2D and moderately impaired kidney function, with reducing racial disparity of metformin use. Further studies to assess impact of metformin label change with longer study period are warranted.