Which of the following is an example of a loop of Henle agent?

Furosemide is classified as a loop diuretic, which acts specifically on the loop of Henle in the nephron of the kidney. It inhibits the sodium-potassium-chloride co-transporter in the ascending limb of the loop of Henle, leading to increased diuresis and natriuresis. This action is particularly effective in managing conditions such as heart failure, where excess fluid retention is a concern, as it helps to reduce blood volume and alleviate symptoms related to fluid overload.

In contrast, hydrochlorothiazide is a thiazide diuretic, which primarily acts on the distal convoluted tubule; spironolactone is an agent that works as an aldosterone antagonist in the distal nephron; and triamterene is a potassium-sparing diuretic that acts on the collecting ducts. None of these directly target the loop of Henle, which clarifies why they do not qualify as loop diuretics.