Which electrolyte abnormality is a known side effect of trimethoprim?

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Multiple Choice

Which electrolyte abnormality is a known side effect of trimethoprim?

Hyperkalemia. Trimethoprim blocks epithelial sodium channels (ENaC) in the collecting duct of the kidney, acting similarly to potassium-sparing diuretics. When ENaC is inhibited, less sodium is reabsorbed and the lumen becomes less negatively charged, which reduces the driving force for potassium secretion into the tubular lumen. The net effect is potassium retention and a rise in serum potassium. This risk is higher in patients with reduced kidney function or when combined with other potassium-raising factors (like certain heart or kidney medications). Monitoring potassium levels is important, and hyponatremia is not the typical hallmark of trimethoprim’s electrolyte effects.

Hyperkalemia. Trimethoprim blocks epithelial sodium channels (ENaC) in the collecting duct of the kidney, acting similarly to potassium-sparing diuretics. When ENaC is inhibited, less sodium is reabsorbed and the lumen becomes less negatively charged, which reduces the driving force for potassium secretion into the tubular lumen. The net effect is potassium retention and a rise in serum potassium. This risk is higher in patients with reduced kidney function or when combined with other potassium-raising factors (like certain heart or kidney medications). Monitoring potassium levels is important, and hyponatremia is not the typical hallmark of trimethoprim’s electrolyte effects.

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