A patient taking Sulfamethoxazole-Trimethoprim develops a significant rise in serum potassium. This is most likely due to the effect of which component?
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Correct answer: Trimethoprim blocking the distal tubule sodium channel
Trimethoprim is structurally related to the potassium-sparing diuretic amiloride and blocks the epithelial sodium channel (ENaC) in the distal nephron. Reduced sodium reabsorption there lowers potassium excretion, so serum potassium rises.
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