A 52-year-old man with type 2 diabetes mellitus and CKD stage 3b (eGFR 38 mL/min) is being reviewed. His HbA1c is 8.4%. Which antidiabetic agent is CONTRAINDICATED in this patient due to the risk of lactic acidosis?

• A Sitagliptin (dose-adjusted)
• B Gliclazide
• C Empagliflozin
• D Metformin ✓

Explanation

Metformin is contraindicated when eGFR falls below 30 mL/min and should be used with caution between 30–45 mL/min (some guidelines hold at <45). At eGFR 38, its use is generally avoided due to accumulation and risk of lactic acidosis. Sitagliptin can be dose-reduced at low eGFR. Gliclazide has predominantly hepatic metabolism and is relatively safer. Empagliflozin should be avoided at eGFR <30 for glycaemic benefit but is used for cardiorenal protection until eGFR <20–25 in some guidelines.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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