A 58-year-old man with type 2 diabetes mellitus on metformin and glipizide presents with a HbA1c of 9.2%. He has stage 3 CKD (eGFR 38 mL/min/1.73 m²) and mild heart failure (EF 40%). Which oral antidiabetic agent should be avoided due to concern for lactic acidosis risk in this patient?
- A Metformin ✓
- B Sitagliptin
- C Empagliflozin
- D Pioglitazone
Correct answer: A. Metformin
Explanation
Metformin is contraindicated when eGFR falls below 30 mL/min/1.73 m² and should be used with caution between 30–45. In this patient with eGFR 38 and heart failure, metformin accumulation elevates the risk of lactic acidosis. SGLT-2 inhibitors like empagliflozin have cardiovascular benefit in heart failure but should not be used below eGFR 20–30 depending on indication; sitagliptin can be dose-reduced safely in CKD.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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