Metformin-Associated Lactic Acidosis in an Older Adult: A Case Report and Review

Metformin is a widely prescribed medication for the management of type 2 diabetes. It is known to have a high safety index; however, it can cause serious adverse effects such as lactic acidosis, particularly in patients with chronic kidney disease. Elderly patients are at higher risk of developing metformin-associated lactic acidosis (MALA) due to aging kidneys. We present an 82-year-old male with a past medical history of diabetes, stage 2 chronic kidney disease, atrial fibrillation on apixaban, stroke, and chronic stage 4 sacral decubitus ulcer who was sent to the emergency department (ED) for altered mental status. He was admitted to the intensive care unit for the management of septic shock, pulseless electrical activity (PEA) cardiac arrest, and acute hypoxemic respiratory failure requiring intubation. Laboratory tests showed lactic acidosis and anion gap metabolic acidosis in the absence of an infectious source. The patient had chronic kidney disease with acute renal failure on metformin. He was diagnosed with MALA. This case highlights the potential risks associated with metformin use in older adults with chronic kidney disease and acute kidney injury from infections, dehydration, and decreasing oral intake due to acute illness, aging, or dementia. There are expected physiological changes in the aging kidney, including cellular dysfunction and nephrosclerosis, that can cause unexpected kidney injury in older adults, causing their estimated glomerular filtration rate (eGFR) to drop acutely. Age-related changes in renal function and decreased clearance of drugs place elderly patients at higher risk of developing MALA. Guidelines for reducing or deprescribing metformin can be considered in older adults. This could prevent morbidity, mortality, and adverse outcomes in frail older adults with diabetes.