Which medication should be avoided in CrCl <30 mL/min due to risk of hyperkalemia and hyponatremia?

• A. Amiloride
• B. Spironolactone
• C. Triamterene
• D. Furosemide

Answer: (A)

In severely reduced kidney function, the risk of dangerous high potassium levels rises with any medication that preserves potassium. Amiloride blocks ENaC channels in the collecting duct, so it directly reduces potassium secretion and sodium reabsorption. In a CrCl below 30, the kidneys are already less able to clear potassium, so adding amiloride can quickly cause hyperkalemia; the altered sodium handling can also contribute to hyponatremia. That combination makes amiloride the one to avoid in this level of kidney impairment.

Loop diuretics like furosemide mainly cause potassium loss (hypokalemia) rather than retention, so they don’t carry the same hyperkalemia risk. Spironolactone and triamterene are also potassium-sparing, but the specific risk profile in very low CrCl makes amiloride the most concerning choice in this scenario. If diuresis is needed, alternative strategies and close electrolyte monitoring are preferred.