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Drug-induced hyperkalaemia — RCPSC IM MCQ

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HardNephrologyDrug-induced hyperkalaemiaRCPSC IM

A 69-year-old man with heart failure is started on spironolactone while taking ramipril and trimethoprim for prostatitis. One week later he develops weakness, bradycardia, potassium 7.4 mmol/L, and creatinine 220 micromol/L. What is the most likely cause?

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Correct answer: B — Combined RAAS blockade and trimethoprim-associated hyperkalaemia

ACE inhibition, mineralocorticoid receptor antagonism, renal dysfunction, and trimethoprim-mediated amiloride-like effects can combine to cause severe hyperkalaemia.

Reference: Hypertension Canada guidance; nephrology medication safety resources