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Spironolactone Most Potent Hyperkalaemia Type 4 RTA — ESENeph MCQ

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ModerateAcid-BaseSpironolactone Most Potent Hyperkalaemia Type 4 RTAESENeph

A 35-year-old man presents with hyperkalaemia (K+ 7.0 mmol/L), metabolic acidosis (bicarbonate 15 mmol/L), and mild AKI (creatinine 180 umol/L). He has type 4 RTA secondary to diabetic nephropathy. His current medications include ramipril and spironolactone. Stopping which medication is MOST likely to resolve the hyperkalaemia?

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Correct answer: C — Spironolactone

While both ramipril and spironolactone contribute to hyperkalaemia, spironolactone is the more potent driver of hyperkalaemia in this context. Spironolactone directly blocks the mineralocorticoid receptor in the collecting duct, preventing aldosterone-mediated potassium secretion via ENaC/ROMK. In a patient with pre-existing type 4 RTA (where aldosterone signalling is already impaired), adding MR blockade dramatically amplifies the potassium retention. Ramipril reduces aldosterone production (via RAAS blockade) but some aldosterone 'escape' occurs. The recommendation is to stop spironolactone first, reassess potassium, and consider reducing (but ideally not stopping) ramipril given its renoprotective benefit. Fludrocortisone may help type 4 RTA but does not address the drug-induced component.

Reference: Palmer 2004 – Type 4 RTA Management; BNF 2024 – Spironolactone Hyperkalaemia