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Informed consent — USMLE Step 3 MCQ

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HardEthics, Patient Safety, Quality Improvement, Systems-Based PracticeInformed consentUSMLE Step 3

A patient taking metformin has eGFR 72 mL/min/1.73 m² and is scheduled for renal angiography with intra-arterial iodinated contrast. Under the FDA prescribing information, what is the medication plan?

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Correct answer: C — Stop metformin at or before contrast, recheck eGFR after 48 hours, and restart if stable

The best answer is “Stop metformin at or before contrast, recheck eGFR after 48 hours, and restart if stable”. The intra-arterial route independently triggers interruption under the FDA label despite an eGFR above 60. The drug is stopped at or before the procedure, renal function is reassessed after 48 hours, and treatment resumes only when eGFR is stable. The FDA label directs clinicians to stop metformin at or before an intra-arterial iodinated-contrast procedure regardless of a preserved baseline eGFR, re-evaluate eGFR after 48 hours, and restart only if renal function is stable. The alternatives use a different threshold, timing, population, or intervention and therefore do not match the clinical facts presented.

Reference: FDA: Glucophage Prescribing Information: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020357s037s039%2C021202s021s023lbl.pdf