Metformin and Iodinated Contrast Agents

Facts about Metformin

• Medication for treatment of type II diabetes
• Decreases hepatic glucose production and enhance glucose uptake in peripheral tissues (by increase insulin sensitivity)
• May be in a pure form or in combination with other antihyperglycemic drugs
• Renal excretion
• Most significant reaction is lactic acidosis, which has a high mortality (up to 50%)
• Most metformin associated lactic acidosis (MALA) occured in patients with coexisting renal dysfunction (high level of metformin due to poor excretion)

Why Do We Worry About Metformin and Iodinated Contrast Agents?

• The use of iodinated contrast agents in patients with pre-existing renal dysfunction can lead to significant contrast-induced nephropathy - that could, in turn, worsen MALA.

In Whom We Should Worry?

• Patients with pre-existing renal dysfunction
• Patients with comorbidities that could give rise to lactic acidosis (liver dysfunction, alcohol abuse, heart failure, myocardial ischemia, peripheral muscle ischemia, sepsis, severe infection)

What To Do?

• Patients with normal renal function and no known comorbidities -> no need to discontinue metformin prior to IV contrast administration
• Patients with known comorbidities -> Discontinue metformin at time of IV contrast administration, and withheld for 48 hours
  
• Patients with known renal dysfunction -> suspend metformin at time of IV contrast administration, renal function follow-ups until safe reinstitution of metformin can be assured

Reference:
American College of Radiology. Manual on Contrast Media version 6 (2008).
McCartney MM, et al. Metformin and contrast media - a dangerous combination? Clin Radiol 1999;54:29.