Metformin Perioperative Management — FRCA Final MCQ
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Correct answer: C — Stop it now and do not restart while the eGFR remains below 30
Explanation lettering: E = shown as A · A = shown as B · D = shown as C · B = shown as D · C = shown as E
D is correct. The decisive feature is the stable eGFR of 18 mL/min/1.73 m², rather than the choice of spinal anaesthesia. UK metformin SmPCs contraindicate metformin when GFR is below 30 mL/min because impaired renal elimination permits drug accumulation and increases the risk of metformin-associated lactic acidosis. It should therefore be stopped now and not restarted while renal function remains below this threshold. Options A and E continue a contraindicated medicine. Options B and C confuse this situation with temporary perioperative interruption in a patient whose renal function otherwise permits metformin; the usual postoperative restart provision cannot override an ongoing renal contraindication. Alternative glucose-lowering treatment and any perioperative insulin requirement should be determined separately from glucose control and fasting status; insulin is not automatically required solely because metformin is discontinued.
Reference: Electronic Medicines Compendium. Metformin 500 mg Tablets, Summary of Product Characteristics, sections 4.2–4.4 (renal impairment and surgery), updated 2025. https://www.medicines.org.uk/emc/product/15731/smpc