Metformin and alcohol binge drinking: a dangerous synergy

Background: Alcoholic ketoacidosis (AKA) is an under-recognised presentation seen in chronic alcoholics with a recent history of binge drinking. Metformin-associated lactic acidosis (MALA) is a rare complication of biguanide treatment which is generally induced by overdose or reduced clearance. Both can present with a significant high anion gap metabolic acidosis and hyperlactataemia. Case report: A 52-year-old man with a background history of chronic alcoholism and type 2 diabetes mellitus (T2DM) treated with metformin only (latest HbA1c7%/ 53 mmol/mol) presented to the hospital with vomiting. He was hypotensive and had acute kidney injury (AKI) stage 3. This presentation occurred after an episode of binge drinking 12 hours prior. He had had three similar episodes in the past, two episodes occurring within 24 hours of binge drinking. Venous blood gas measurement on presentation showed a pH of 6.934, lactate of 16 mmol/L and glucose of 21.7 mmol/L, and bedside ketones were 3.2 mmol/L. He was treated according to the hospital diabetic ketoacidosis (DKA) protocol. Discussion: In the presence of a recurrent history of DKA in a patient with chronic alcoholism, AKA should be considered. The mechanism of AKA is complex and occurs in the setting of insulin deficiency and excess glucagon release. Excess ethanol metabolism favours the formation of beta-hydroxybutyrate ketoacid. Counter-regulatory hormones and volume depletion drive lipolysis and ketosis. Repeated episodes of binge drinking-induced renal impairment may have caused metformin accumulation, resulting in hyperlactataemia.