Metformin Toxicity in Acute Kidney Injury. A Rare Cause of Severe Lactic Acidosis

Abstract

Metformin a biguanide derivative is the preferred initial pharmacologic agent for the treatment of type 2 diabetes mellitus per current guidelines of the American Diabetes Association. It is prescribed to an estimated 120 million people worldwide. Type B lactic acidosis is a reported but rare side effect of Metformin use. Serum Metformin level is not routinely monitored or available in most hospitals, but it can be a useful test to confirm the diagnosis and guide future use of Metformin in at risk patients. We present a case of a 78-year old African American diabetic female on prescribed dose of Metformin with no history of kidney disease who presented with acute encephalopathy and hemodynamic instability. Her laboratory data showed acute kidney injury (AKI) with severe lactic acidosis (LA). She required large amount of intravenous bicarbonate infusions and urgent initiation of Continuous Veno-Venous Hemodialysis (CVVHD) due to severe refractory metabolic acidosis. Her serum Metformin level sent 12 hours after initiation of CVVHD was still critically elevated at 19 mcg/ml. Her acidosis and AKI started to resolve after 48 hours of CVVHD with resolution of encephalopathy as well. Her renal function returned to baseline and she was eventually discharged home, but Metformin was not resumed back.