Pharmacy PEBC Practice Exam

How do loop diuretics function?

1. By promoting the reabsorption of sodium and chloride

2. By inhibiting sodium and chloride reabsorption in the ascending loop of Henle

3. By blocking the release of aldosterone

4. By increasing blood volume

The correct answer is: By inhibiting sodium and chloride reabsorption in the ascending loop of Henle

Loop diuretics function primarily by inhibiting the reabsorption of sodium and chloride in the ascending loop of Henle, which is a key segment of the nephron in the kidney. This mechanism is critical because the ascending loop is responsible for the reabsorption of a significant portion of sodium and chloride from the filtrate back into the bloodstream. When loop diuretics block this reabsorption process, it results in increased concentrations of sodium and chloride in the tubular fluid, leading to osmotic diuresis. As a consequence, more water is retained within the tubular lumen, resulting in increased urine output. This specific action helps reduce fluid overload in conditions such as heart failure, edema, and certain kidney disorders. By directly targeting the ascending loop of Henle, loop diuretics effectively lower blood volume and blood pressure through their diuretic effect. Importantly, this mechanism distinguishes loop diuretics from other types of diuretics that may target different areas of the nephron or work through different physiological pathways, such as influencing hormonal activity or promoting sodium reabsorption.