Diuretics — MCQs

Diuretics Indian Medical PG Practice Questions and MCQs

Question 211: A 50-year-old man has a history of frequent episodes of renal colic with high calcium renal stones. The most useful diuretic in the treatment of recurrent calcium stones is:

A. Furosemide
B. Hydrochlorothiazide (Correct Answer)
C. Acetazolamide
D. Spironolactone

Explanation: ***Hydrochlorothiazide*** - **Thiazide diuretics** reduce urinary calcium excretion by increasing calcium reabsorption in the distal convoluted tubule. - This mechanism makes them effective in preventing the recurrence of **calcium oxalate** and **calcium phosphate kidney stones**. *Furosemide* - **Loop diuretics** like furosemide increase urinary calcium excretion, which would *aggravate* rather than prevent calcium stone formation. - This effect is due to inhibiting sodium-potassium-chloride reabsorption in the **loop of Henle**, thereby reducing calcium reabsorption. *Spironolactone* - **Spironolactone** is a potassium-sparing diuretic that acts as an aldosterone antagonist, primarily affecting sodium and potassium balance. - It does not significantly impact urinary calcium excretion, and therefore, it is **not indicated** for the prevention of calcium renal stones. *Acetazolamide* - **Acetazolamide** is a carbonic anhydrase inhibitor that increases bicarbonate excretion and causes a metabolic acidosis. - It increases urinary pH and can potentially *promote* the formation of calcium phosphate stones in susceptible individuals.

Question 212: Which of the following statements about the PRIMARY mechanism of action of acetazolamide is correct?

A. It causes metabolic alkalosis
B. It decreases potassium excretion
C. Has structural resemblance to penicillins
D. Reversible inhibitor of carbonic anhydrase (Correct Answer)

Explanation: ***Reversible inhibitor of carbonic anhydrase*** - Acetazolamide is a **carbonic anhydrase inhibitor** that primarily acts by reducing the reabsorption of bicarbonate in the proximal tubule of the kidney. - This inhibition leads to increased urinary excretion of **bicarbonate, sodium, and water**, ultimately reducing intraocular pressure, intracranial pressure, and systemic fluid retention. *It decreases potassium excretion* - Acetazolamide actually **increases potassium excretion** indirectly by increasing the delivery of sodium and bicarbonate to the collecting duct, which enhances potassium secretion. - This can lead to **hypokalemia** with prolonged use. *It causes metabolic alkalosis* - Acetazolamide causes **metabolic acidosis**, not alkalosis, because it inhibits the reabsorption of bicarbonate in the renal tubules, leading to increased bicarbonate excretion and a decrease in serum bicarbonate levels. - This effect makes it useful in treating metabolic alkalosis, but it does not cause it. *Has structural resemblance to penicillins* - Acetazolamide is a **sulfonamide derivative** and does not have a structural resemblance to penicillins. - Its mechanism of action is completely distinct from that of antibiotics in the penicillin class.

Question 213: Select the diuretic that is most effective in acute angle-closure glaucoma.

A. Furosemide
B. Amiloride
C. Indapamide
D. Mannitol (Correct Answer)

Explanation: ***Mannitol*** - **Mannitol** is an osmotic diuretic that creates an osmotic gradient, drawing fluid from the eye into the bloodstream, thereby **rapidly reducing intraocular pressure (IOP)**. - Its quick onset of action and potent IOP-lowering effect make it the **drug of choice for acute angle-closure glaucoma** when rapid pressure reduction is critical. *Furosemide* - **Furosemide** is a loop diuretic that primarily acts on the renal tubules to increase urine output, with **minimal direct effect on intraocular pressure**. - While it can lower systemic blood pressure, its efficacy in **rapidly reducing elevated IOP in acute glaucoma is limited** compared to osmotic agents. *Amiloride* - **Amiloride** is a potassium-sparing diuretic that works in the collecting ducts of the kidneys and is primarily used for **hypertension and heart failure**, often in combination with other diuretics. - It does not have a significant or rapid effect on **intraocular pressure**, making it ineffective for acute angle-closure glaucoma. *Indapamide* - **Indapamide** is a thiazide-like diuretic that acts on the distal convoluted tubule and is primarily used for the treatment of **hypertension and edema**. - It has a slower onset of action and **does not effectively reduce intraocular pressure** in acute settings, making it unsuitable for acute angle-closure glaucoma.

Practice by Chapter

Carbonic Anhydrase Inhibitors

Practice Questions

Loop Diuretics

Practice Questions

Thiazide and Thiazide-Like Diuretics

Practice Questions

Potassium-Sparing Diuretics

Practice Questions

Carbonic Anhydrase Inhibitors

Practice Questions

Osmotic Diuretics

Practice Questions

Combination Diuretic Therapy

Practice Questions

Diuretics in Heart Failure

Practice Questions

Diuretics in Hypertension

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Diuretics in Renal Disorders

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Adverse Effects and Drug Interactions

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Diuretics — MCQs

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