American Society of Radiologic Technologist (ASRT) Practice Exam

What medication should be withheld from diabetic patients on the day of an iodinated contrast study?

1. Furosemide (Lasix)

2. Insulin

3. Metformin

4. Diphenhydramine hydrochloride (Benadryl)

The correct answer is: Metformin

Withholding metformin from diabetic patients the day of an iodinated contrast study is crucial due to the risk of lactic acidosis, particularly in patients with compromised renal function. Iodinated contrast agents can lead to contrast-induced nephropathy, which negatively affects kidney function. If kidney function is impaired, metformin, which is primarily excreted through the kidneys, may accumulate in the bloodstream, increasing the risk for the development of lactic acidosis. The standard guideline is to stop metformin at the time of the imaging procedure and not to resume it until at least 48 hours post-procedure, provided renal function is stable. This ensures that the patient’s safety is prioritized, especially in the context of potential renal impairment caused by the contrast dye. While insulin and other medications may need adjustments, they do not carry the same direct risk of lactic acidosis when used in conjunction with iodinated contrast. Other medications like furosemide may be used as needed and diphenhydramine is usually irrelevant in this specific context. Hence, it is metformin that requires careful management in conjunction with iodinated contrast studies to minimize potential complications.