A patient with a history of severe contrast allergy and diabetes mellitus on metformin is scheduled for a contrast-enhanced CT of the abdomen. Regarding metformin and iodinated contrast media, the primary concern is:

• A Risk of lactic acidosis if contrast-induced acute kidney injury develops ✓
• B Anaphylaxis from a drug-contrast interaction
• C Metformin reducing contrast enhancement quality
• D Nephrotoxicity from combined metformin and contrast exposure

Explanation

Metformin is renally excreted and inhibits mitochondrial complex I, predisposing to lactic acidosis if renal function deteriorates. Iodinated contrast media can cause contrast-induced acute kidney injury (CI-AKI), which impairs metformin excretion, leading to accumulation and life-threatening lactic acidosis. Current guidelines recommend withholding metformin from the time of contrast administration until 48 hours afterward, with reassessment of renal function before restarting, particularly in patients with eGFR below 60 mL/min/1.73m². This is a pharmacological, not immunological, interaction.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.