Metformin in patients with chronic kidney disease: strengths and weaknesses.

A wide array of benefits has been attributed to metformin. These include attenuation of abnormal glucose metabolism (diabetes treatment and prevention), weight neutrality or weight loss, improvement in the pathophysiologic components of metabolic syndrome (insulin resistance, subclinical inflammation, and endothelial dysfunction), lipid-lowering properties, cardiovascular protection, and antineoplastic potential. Metformin itself is not a nephrotoxic drug. Initially appointed as the safest hypoglycemic agent in chronic kidney disease, its use has been limited in these patients because of the perceived risk of lactic acidosis. A fear perpetuated by numerous case reports in which it is implicated. Current guidelines stipulate that it must be used with caution in estimated glomerular filtration rates (eGFRs) of less than 60 mL/minute and not at all in eGFRs of less than 30 mL/minute. Identified risk factors for metformin-associated lactic acidosis include acute kidney injury, hypoxemia, sepsis, alcohol abuse, liver failure, myocardial infarction, and shock. Treatment may include supportive care and dialysis techniques. On the other hand, it is likely that the use of metformin would be beneficial in many with chronic kidney disease according to the advantages associated with attenuation of metabolic syndrome and cardiovascular protection. The reality of severe metformin-induced lactic acidosis in the absence of chronic renal impairment raises the question of limitation of its use in these patients.