Articles: Metformin & Lactic Acidosis
Metformin & Lactic Acidosis:
CKD, Type 2 Diabetes, and Drug Interactions
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Metformin use is contraindicated, per current FDA prescribing information, in men with a serum creatinine (SCr) ≥1.5 mg/dL and in women with a SCr ≥1.4 mg/dL. Metformin should also be used cautiously in patients with conditions that interfere with the metabolism and excretion of lactic acid, such as heart failure, liver disease, and during times of acute illness. Lactic acidosis is known to occur in people with diabetes regardless of metformin use, and the role of metformin in contributing to lactic acidosis is increasingly controversial. Metformin use, however, may be a predisposing factor in the context of serious illness.
Despite these concerns and published case reports of metformin-associated lactic acidosis (MALA), current data indicate the overall risk of MALA is low. It has been suggested that estimated glomerular filtration rate (eGFR) may be a more appropriate measure to assess continued metformin use when compared to SCr as it can translate into widely varying eGFR levels depending on race, age, and muscle mass. A recent review proposed metformin use should be reevaluated at an eGFR <45 mL/min/1.73 m2 with a reduction in maximum dose to 1,000 mg per day and discontinued when <30 mL/min/1.73 m2.
In the case of MK, a review of her laboratory history indicated that her eGFR had been stable for a number of years. While her physician was agreeable to her continuing metformin at 1,000 mg/day, MK elected to discontinue the medication with the permission of her PCP due to the MALA risk.
Michael Wyant, PharmD Candidate 2016
Washington State University
Spokane, Washington
Joshua J. Neumiller, PharmD, CDE, FASCP
Assistant Professor
Washington State University
Spokane, Washington
