Is metformin associated with acute kidney injury? A case-control study of patients with type 2 diabetes admitted with acute infection

INTRODUCTION: Despite the long-term renoprotective effects of Metformin, a recent study on data from the U.S. Food and Drug Administration reported a possible nephrotoxic effect, contributing to the development of acute kidney injury (AKI). We investigated the association between metformin and AKI in patients admitted with the AKI-prone condition of acute infection and compared results with corresponding results of other antidiabetics.

METHODS: In a nationwide register-based case-control study, we identified Danish patients with type 2 diabetes hospitalized with acute infection between 2008 and 2018. Cases of AKI had an increase in plasma creatinine ≥  × 1.5 during admission, controls did not. Antidiabetics were identified up to 6 months before admission. Odds ratio (OR) of each antidiabetic was computed in separate multiple logistic regression models adjusted for relevant medication and comorbidities and results compared.

RESULTS: We included 46,811 patients, hereof 9454 AKIs (20%) and 2186 (4.7%) severe AKIs. Overall, 56% were males, median age (IQR) was 73 (65-81). Sixty percent received metformin, 13% sulfonylurea, 31% insulin and 8% dipeptidyl peptidase-4 inhibitors (DPP-4i), with equal distribution between cases and controls. Metformin was associated with increased OR (CI) for AKI, 1.07 (1.02-1.12), equally to sulfonylurea, 1.10 (1.03-1.18) and DPP-4i, 1.11 (1.02-1.20), but not insulin, 0.99 (0.93-1.05). In severe AKI, results for metformin were 1.27 (1.25-1.40) but increased equivalently to other antidiabetics.

CONCLUSIONS: In patients with type 2 diabetes hospitalized with acute infection, metformin was not independently associated with AKI, since other antidiabetics were also significantly associated, indicating confounding by indication.