Surprise quiz: metformin overdose

December 18, 2012, 11:53 pm


Metformin-Associated Lactic Acidosis (MALA): Case Files of the Einstein Medical Center Medical Toxicology Fellowship. Kopec KT, Kowalski MJ. J Med Toxicol 2012 Dec 12 {Epub ahead of print]

No abstract available

This case-based review of metformin-associated metabolic acidosis (MALA) is concise and worth reading. The following is a surprise quiz based on some of the points made in the article. (Click on the question to reveal the answer.)

  • decreased gluconeogenesis
  • increased peripheral glucose uptake
  • decreased fatty acid oxidation

  • renal failure
  • hepatic failure
  • alcohol abuse
  • history of lactic acidosis
  • pregnancy
  • cardiac or respiratory insufficiency

  1. Type A – caused by decreased perfusion, hypoxia, or increased lactate production
  2. Type B – caused by metabolic derangements (including metformin toxicity0

Metformin is primarily excreted unchanged in the urine.

  • acute renal insufficiency (for instance, after administration of intravenous contrast)
  • dehydration
  • sepsis
  • shock
  • acidosis

  • abdominal pain
  • nausea
  • vomiting
  • fatigue
  • myalgias
  • altered mental status
  • myocardial insufficiency

  1. removal of metformin
  2. correction of acid-base imbalance

Since metformin is water soluble, quickly distributes to the tissues, and has a large volume of distribution, it is most beneficial to institute HD early while the drug is still in the blood.

Dialyzing using a sodium bicarbonate buffer may help correct acid-base imbalance as well as increase metformin clearance.

A single abstract did not show benefit (J Clin Toxicol 2011;49:515). I would not expect this to be effective since metformin is highly water-soluble.

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