Metformin lactic acidosis. Report of two cases

Metformin is recommended as a first-line treatment for patients with diabetes mellitus type 2; it has a cardiovascular protective effect, and low risk of hypoglycemia. However, a severe but infrequent complication of its use is lactic acidosis, which has high morbidity and mortality rates. The estimated incidence of metformin lactic acidosis is 7,4 cases per 100.000 patients per year. Main risk factors are acute or chronic renal disease, congestive heart failure, hepatic failure, and concomitant use of drugs that affect mettormin clearance or energy metabolism. Treatment includes hydration with crystalloids, support measures, and intravenous bicarbonate. Penal replacement therapy has been successful for treating metformin-associated lactic acidosis, but there are still no clear indications for it, because metformin is a partially dialyzable molecule and prolonged hemodialysis is required to reduce its levels sufficiently. Despite current treatment, mortality remains high. Early diagnosis and prompt multidisciplinary support are essential to improve outcome in these patients.