Iodinated Contrast and Metformin

Lactic acidosis is a rare metabolic complication which can occur due to metformin accumulation in patients with renal impairment. The risk of lactic acidosis increases with the degree of renal dysfunction and the patient's age. Lactic acidosis is a medical emergency and must be treated in hospital immediately.

Patients receiving intravascular iodinated contrast may experience an acute deterioration in renal function leading to metformin accumulation and potential lactic acidosis. There is no evidence for a direct interaction between metformin and iodinated contrast agents.

At Hunter Radiology we use the RANZCR guideline for the Administration of Iodinated Contrast Media.

The Guideline for administering IV Contrast to diabetic patients taking Metformin is:

• In diabetic patients taking metformin, consider the risks of lactic acidosis and the potential benefits of the procedure.

• In patients with normal renal function, Metformin does not need to be stopped providing that a moderate amount of contrast is used (100mL or less*), which would be unlikely to result in contrast induced nephropathy in the patient.

• In patients with renal impairment, Metformin should be withheld for at least 48 hours commencing on the day of the contrast study.

It is very helpful for Hunter Radiology to have a recent eGFR result on the referral so we can assess the degree of renal function of the patient when we are considering Iodinated Contrast administration.

For more information see the RANZCR GUIDELINES FOR IODINATED CONTRAST ADMINISTRATION