Co-prescription of metformin and glucagon-like peptide-1 receptor agonists and metformin-associated lactic acidosis: A case series.

This case series describes four critically ill patients with type 2 diabetes mellitus who developed metformin-associated lactic acidosis (MALA) in the context of co-prescription of high-dose metformin with either a GLP-1 receptor agonist or a dual GIP/GLP-1 receptor agonist. In each case, MALA appeared to be precipitated by the introduction or dose escalation of the incretin-based therapy, or by an acute gastrointestinal illness occurring while the patient was on a maintenance GLP-1 receptor agonist dose. All four patients required acute renal replacement therapy. The authors propose that the shared gastrointestinal side-effect profile of these drug classes—including nausea, vomiting, decreased appetite, and abdominal pain—may contribute to dehydration and impaired renal metformin clearance, thereby elevating the risk of MALA. The study is limited by its small sample size (n=4), lack of a comparison group, and the inherent reporting biases of a case series design. The authors conclude that clinicians should exercise caution when co-prescribing these medication classes, with attention to kidney function monitoring and patient education on sick-day management rules.

Why this grade: A case series of only four patients with no control group provides limited, hypothesis-generating human evidence of a potential drug-drug interaction signal, but cannot establish causation or incidence.