Which medication should be discontinued prior to a CT scan with contrast?

Discontinuing metformin prior to a CT scan with contrast is important because of the risk of lactic acidosis, particularly in patients with impaired renal function. Contrast agents can potentially cause acute kidney injury, and if kidney function declines, metformin can accumulate in the body, leading to this serious complication.

Patients undergoing procedures with contrast should have their renal function evaluated beforehand. If there is concern for renal impairment or if the patient has an estimated glomerular filtration rate (eGFR) below a certain threshold (commonly 30 mL/min), metformin should be held for at least 48 hours before and after the administration of contrast media. This practice helps to ensure patient safety and minimizes the risk of potential adverse effects associated with the use of metformin in the setting of contrast-induced nephropathy.

Other medications listed typically do not require discontinuation before a contrast CT scan. Aspirin and warfarin are anti-platelet and anticoagulant medications, respectively, and while they may increase bleeding risk, they do not specifically contraindicate the use of contrast. Lisinopril, an ACE inhibitor, does not need to be discontinued because it does not significantly increase the risk of nephrotoxicity associated with contrast media in