Diuretics are an important class of drugs in pharmacology that increase urine formation by promoting the excretion of sodium and water through the kidneys. They are widely used in the management of hypertension, edema, heart failure, and certain other medical conditions.
For pharmacy students, understanding the classification, mechanism of action, therapeutic uses, and adverse effects of diuretics is essential for examinations such as GPAT, D.Pharm, B.Pharm, and pharmacist recruitment examinations.
In this article, you will find 30 important multiple-choice questions (MCQs) on diuretics, along with correct answers and explanations for quick revision.
Classification of Diuretics: Quick Revision
Before attempting the MCQs, revise these major classes of diuretics.
- Loop diuretics: Furosemide, bumetanide, torsemide.
- Thiazide and thiazide-like diuretics: Hydrochlorothiazide, chlorthalidone, indapamide.
- Potassium-sparing diuretics: Spironolactone, eplerenone, amiloride, triamterene.
- Carbonic anhydrase inhibitors: Acetazolamide.
- Osmotic diuretics: Mannitol.
- ADH antagonists (aquaretic drugs): Tolvaptan and conivaptan.
📝30 Important MCQs on Diuretics
1. Which of the following is a loop diuretic?
A. Hydrochlorothiazide
B. Furosemide
C. Spironolactone
D. Acetazolamide
Correct Answer: B. Furosemide
Explanation: Furosemide is a loop diuretic that acts on the thick ascending limb of the loop of Henle. It inhibits sodium, potassium, and chloride reabsorption, producing powerful diuresis.
2. Loop diuretics inhibit which transporter?
A. Na⁺/Cl⁻ cotransporter
B. Na⁺/K⁺/2Cl⁻ cotransporter
C. Na⁺/H⁺ exchanger only
D. Epithelial sodium channel
Correct Answer: B. Na⁺/K⁺/2Cl⁻ cotransporter
Explanation: Loop diuretics inhibit the NKCC2 transporter in the thick ascending limb, reducing sodium chloride reabsorption and increasing urinary electrolyte excretion.
3. Which diuretic is commonly associated with hypokalemia?
A. Spironolactone
B. Amiloride
C. Furosemide
D. Eplerenone
Correct Answer: C. Furosemide
Explanation: Loop diuretics increase sodium delivery to the distal nephron and can increase potassium excretion. This may result in hypokalemia.
4. Thiazide diuretics primarily act on which part of the nephron?
A. Proximal convoluted tubule
B. Thick ascending limb
C. Early distal convoluted tubule
D. Collecting duct
Correct Answer: C. Early distal convoluted tubule
Explanation: Thiazides inhibit the sodium-chloride cotransporter in the early distal convoluted tubule, increasing sodium and water excretion.
5. Which transporter is inhibited by hydrochlorothiazide?
A. NKCC2
B. NCC
C. ENaC
D. SGLT2
Correct Answer: B. NCC
Explanation: Hydrochlorothiazide inhibits the sodium-chloride cotransporter (NCC) in the distal convoluted tubule.
6. Which diuretic can increase calcium reabsorption in the kidneys?
A. Furosemide
B. Hydrochlorothiazide
C. Mannitol
D. Acetazolamide
Correct Answer: B. Hydrochlorothiazide
Explanation: Thiazide diuretics reduce urinary calcium excretion and can increase calcium reabsorption. They may be useful in selected patients with recurrent calcium kidney stones and hypercalciuria.
7. Which of the following is a potassium-sparing diuretic?
A. Torsemide
B. Bumetanide
C. Amiloride
D. Chlorthalidone
Correct Answer: C. Amiloride
Explanation: Amiloride blocks epithelial sodium channels (ENaC) in the late distal nephron and collecting duct, reducing potassium secretion.
8. Spironolactone acts by blocking which receptor?
A. Beta-1 adrenergic receptor
B. Mineralocorticoid receptor
C. Histamine H1 receptor
D. Muscarinic receptor
Correct Answer: B. Mineralocorticoid receptor
Explanation: Spironolactone blocks aldosterone receptors, reducing sodium reabsorption and potassium excretion. It is used in conditions such as heart failure, primary hyperaldosteronism, and resistant hypertension in selected patients.
9. Which adverse effect is particularly associated with spironolactone?
A. Hypokalemia
B. Gynecomastia
C. Ototoxicity
D. Severe hypocalcemia
Correct Answer: B. Gynecomastia
Explanation: Spironolactone can cause gynecomastia and sexual or menstrual adverse effects because it also interacts with androgen and progesterone receptors. Eplerenone has fewer antiandrogenic effects.
10. Which diuretic inhibits carbonic anhydrase?
A. Acetazolamide
B. Furosemide
C. Spironolactone
D. Mannitol
Correct Answer: A. Acetazolamide
Explanation: Acetazolamide inhibits carbonic anhydrase in the proximal tubule, increasing bicarbonate excretion and producing alkaline urine.
11. Acetazolamide is particularly useful in which condition?
A. Acute mountain sickness
B. Bacterial pneumonia
C. Iron-deficiency anemia
D. Hypothyroidism
Correct Answer: A. Acute mountain sickness
Explanation: Acetazolamide helps prevent and treat acute mountain sickness by promoting renal bicarbonate loss and stimulating ventilation through a mild metabolic acidosis.
12. Which of the following is an osmotic diuretic?
A. Mannitol
B. Eplerenone
C. Indapamide
D. Amiloride
Correct Answer: A. Mannitol
Explanation: Mannitol is filtered by the glomerulus and increases tubular fluid osmolality, reducing water reabsorption. It is used in selected cases of raised intracranial pressure and raised intraocular pressure.
13. Mannitol should generally be avoided in which condition?
A. Pulmonary edema
B. Selected cases of raised intracranial pressure
C. Selected cases of raised intraocular pressure
D. Certain neurosurgical emergencies
Correct Answer: A. Pulmonary edema
Explanation: Mannitol initially expands the extracellular fluid volume by drawing water into the bloodstream. It can worsen pulmonary edema or heart failure, particularly in susceptible patients.
14. Which diuretic is associated with ototoxicity, especially at high doses or with rapid intravenous administration?
A. Furosemide
B. Amiloride
C. Spironolactone
D. Acetazolamide
Correct Answer: A. Furosemide
Explanation: Loop diuretics can cause hearing-related toxicity, particularly with high doses, rapid intravenous administration, severe renal impairment, or concurrent use of other ototoxic drugs.
15. Which electrolyte abnormality is a major concern with potassium-sparing diuretics?
A. Hyperkalemia
B. Hypernatremia
C. Hypocalcemia
D. Hypermagnesemia
Correct Answer: A. Hyperkalemia
Explanation: Spironolactone, eplerenone, amiloride, and triamterene can increase serum potassium. The risk is higher in renal impairment or when combined with other drugs that raise potassium.
16. Which diuretic is commonly used to manage edema associated with heart failure?
A. Furosemide
B. Acetazolamide for every patient
C. Mannitol for routine long-term treatment
D. Amiloride as the only treatment in all cases
Correct Answer: A. Furosemide
Explanation: Loop diuretics such as furosemide reduce fluid congestion in patients with heart failure. Treatment choice and dose depend on the patient’s clinical condition and kidney function.
17. Which diuretic class is commonly used as a first-line option for uncomplicated hypertension?
A. Thiazide or thiazide-like diuretics
B. Osmotic diuretics
C. Carbonic anhydrase inhibitors
D. Loop diuretics in every patient
Correct Answer: A. Thiazide or thiazide-like diuretics
Explanation: Thiazide and thiazide-like diuretics are established options for hypertension. The choice depends on the patient’s clinical characteristics and current treatment guidelines.
18. Which diuretic may cause metabolic alkalosis?
A. Furosemide
B. Acetazolamide
C. Amiloride
D. Spironolactone
Correct Answer: A. Furosemide
Explanation: Loop diuretics can increase hydrogen ion and potassium loss, contributing to metabolic alkalosis. Acetazolamide, by contrast, can cause metabolic acidosis.
19. Which diuretic is most likely to cause metabolic acidosis?
A. Acetazolamide
B. Hydrochlorothiazide
C. Furosemide
D. Bumetanide
Correct Answer: A. Acetazolamide
Explanation: Acetazolamide increases bicarbonate excretion in urine. The resulting bicarbonate loss can cause hyperchloremic metabolic acidosis.
20. Which diuretic class may increase uric acid levels and precipitate gout?
A. Thiazide diuretics
B. Potassium-sparing diuretics in every patient
C. Carbonic anhydrase inhibitors in every patient
D. ADH antagonists
Correct Answer: A. Thiazide diuretics
Explanation: Thiazides can reduce uric acid excretion and increase serum uric acid. Loop diuretics can also cause hyperuricemia.
21. Which of the following is a thiazide-like diuretic?
A. Indapamide
B. Mannitol
C. Acetazolamide
D. Triamterene
Correct Answer: A. Indapamide
Explanation: Indapamide is a thiazide-like diuretic used primarily for hypertension and, in some settings, edema.
22. Which diuretic directly blocks epithelial sodium channels?
A. Amiloride
B. Spironolactone
C. Furosemide
D. Hydrochlorothiazide
Correct Answer: A. Amiloride
Explanation: Amiloride blocks ENaC in the late distal nephron and collecting duct. Spironolactone and eplerenone instead block mineralocorticoid receptors.
23. Which diuretic is a selective aldosterone receptor antagonist?
A. Eplerenone
B. Mannitol
C. Acetazolamide
D. Torsemide
Correct Answer: A. Eplerenone
Explanation: Eplerenone selectively blocks mineralocorticoid receptors and has fewer antiandrogenic effects than spironolactone. It can still cause hyperkalemia.
24. Which diuretic is used to reduce intraocular pressure in selected clinical situations?
A. Mannitol
B. Spironolactone
C. Amiloride
D. Triamterene
Correct Answer: A. Mannitol
Explanation: Intravenous mannitol can lower intraocular pressure by creating an osmotic gradient that draws water out of the eye. Its use depends on the clinical situation.
25. Which diuretic class is generally the most potent in terms of sodium excretion?
A. Loop diuretics
B. Potassium-sparing diuretics
C. Carbonic anhydrase inhibitors
D. Thiazides in every clinical situation
Correct Answer: A. Loop diuretics
Explanation: Loop diuretics can produce substantial natriuresis because the thick ascending limb reabsorbs a large proportion of filtered sodium. The response depends on kidney function, dose, and other clinical factors.
26. Which combination increases the risk of hyperkalemia?
A. Spironolactone and an ACE inhibitor
B. Furosemide and a thiazide
C. Acetazolamide and mannitol
D. Hydrochlorothiazide and indapamide
Correct Answer: A. Spironolactone and an ACE inhibitor
Explanation: Both spironolactone and ACE inhibitors can raise serum potassium. Their combination may be appropriate for selected patients but requires medical supervision and potassium and renal-function monitoring.
27. Which diuretic can be useful in selected cases of nephrogenic diabetes insipidus?
A. Hydrochlorothiazide
B. Mannitol
C. Furosemide alone
D. Eplerenone alone
Correct Answer: A. Hydrochlorothiazide
Explanation: Thiazides can paradoxically reduce urine volume in nephrogenic diabetes insipidus. They are used as part of a management plan that may also include dietary sodium reduction and treatment of the underlying cause.
28. Which of the following is an important adverse effect of loop and thiazide diuretics?
A. Volume depletion
B. Increased blood volume in all patients
C. Permanent immunity to infection
D. Increased oxygen production
Correct Answer: A. Volume depletion
Explanation: Excessive diuresis can cause dehydration, low blood pressure, dizziness, and worsening kidney function. Electrolytes and kidney function may need monitoring during treatment.
29. Tolvaptan acts primarily by blocking which receptor?
A. V2 vasopressin receptor
B. Beta-2 receptor
C. H1 histamine receptor
D. Alpha-1 receptor
Correct Answer: A. V2 vasopressin receptor
Explanation: Tolvaptan blocks vasopressin V2 receptors in the collecting duct, increasing free-water excretion. It is an aquaretic drug used in selected patients, including certain cases of hyponatremia, under appropriate monitoring.
30. Which statement about diuretics is correct?
A. All diuretics cause potassium loss
B. All diuretics are used only for hypertension
C. Different diuretic classes act at different sites in the nephron
D. Diuretics never affect electrolyte balance
Correct Answer: C. Different diuretic classes act at different sites in the nephron
Explanation: Diuretic classes have different mechanisms, uses, and adverse effects. Loop diuretics and thiazides can increase potassium loss, whereas potassium-sparing drugs may cause hyperkalemia.
High-Yield Exam Revision Points
- Furosemide: Loop diuretic; inhibits NKCC2.
- Hydrochlorothiazide: Thiazide diuretic; inhibits NCC.
- Spironolactone: Mineralocorticoid receptor antagonist; may cause gynecomastia and hyperkalemia.
- Amiloride: Blocks epithelial sodium channels.
- Acetazolamide: Carbonic anhydrase inhibitor; may cause metabolic acidosis.
- Mannitol: Osmotic diuretic; used in selected cases of raised intracranial or intraocular pressure.
- Thiazides: Reduce urinary calcium excretion and may increase uric acid.
- Loop diuretics: Can cause hypokalemia, volume depletion, and ototoxicity.
- Tolvaptan: Vasopressin V2 receptor antagonist; promotes free-water excretion.
- Important monitoring: Blood pressure, kidney function, fluid status, and serum electrolytes.
📋Frequently Asked Questions (FAQs)
1. Which diuretic is the most potent?
Loop diuretics, such as furosemide, generally produce the greatest increase in sodium excretion among the major diuretic classes.
2. Which diuretics are potassium-sparing?
Spironolactone, eplerenone, amiloride, and triamterene are potassium-sparing diuretics.
3. Which diuretic is used in glaucoma?
Mannitol can be used to lower intraocular pressure in selected acute situations. Acetazolamide can also lower intraocular pressure in appropriate clinical settings.
4. Which diuretic is associated with gynecomastia?
Spironolactone is associated with gynecomastia because of its effects on sex-hormone receptors.
5. Why are diuretics important in pharmacy examinations?
Diuretics are frequently studied because their classification, mechanisms, sites of action, therapeutic uses, and adverse effects are fundamental pharmacology topics.
🎯 Conclusion
Diuretics are important drugs that increase the excretion of sodium and water through the kidneys. Understanding their mechanisms, sites of action, therapeutic uses, and adverse effects is essential for pharmacy examinations and pharmacology revision.
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