The Poison Review

Can acute overdose of metformin lead to lactic acidosis? Wills BK et al. Amer J Emerg Med 2010;28:857.

Abstract

Metformin-associated lactic acidosis (MALA) is usually described in the setting of chronic therapeutic dosing in a patient with a c0-morbidity or contraindication to use of the drug, such as renal failure.  There is some disagreement in the literature as to whether MALA can be caused by acute metformin overdose.  These authors searched the electronic medical records of two large poison centers (Illinois and Washington state) and identified 12 cases of lactic acidosis following acute overdose with metformin alone, without evidence in the records for co-morbidities or co-ingestions.

Despite the debate in the literature, it seems clear to me that MALA can be caused by acute overdose alone — although this is rare, and most metformin overdose patients do well with supportive care.  This study suffers from all the weaknesses inherent in reviews of electronic poison center records, including incomplete data collection.  However, I agree with the authors’ conclusion that: “Apparent metformin mono-overdose is associated with MALA”.