Diuretics — MCQs
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Which drug causes deafness?
Which of the following diuretics results in the minimum net excretion of filtered sodium?
What is the drug of choice for familial hyperkalemic periodic paralysis?
Carbonic anhydrase inhibitors lead to all of the following except?
Which one of the following is not an adverse effect of ACE inhibitors?
All of the following drugs act as potassium-sparing diuretics, EXCEPT:
Which of the following is a potassium-sparing drug?
Which of the following are potassium-sparing diuretics?
Which of the following is true about acetazolamide?
Which of the following is a false statement regarding thiazide diuretics?
Diuretics Indian Medical PG Practice Questions and MCQs
Question 51: Which drug causes deafness?
- A. Thiazide
- B. Spironolactone
- C. Ethacrynic acid (Correct Answer)
- D. Triamterene
Explanation: **Explanation:** The correct answer is **Ethacrynic acid**. **Mechanism of Ototoxicity:** Ethacrynic acid is a potent **Loop Diuretic** (High-ceiling diuretic). These drugs inhibit the $Na^+/K^+/2Cl^-$ symporter in the Thick Ascending Limb of the Loop of Henle. However, a similar transport system exists in the **stria vascularis** of the inner ear, which maintains the ionic composition of endolymph. Inhibition of these transporters leads to electrolyte imbalances in the inner ear, resulting in sensorineural hearing loss (ototoxicity) and tinnitus. **Analysis of Options:** * **Ethacrynic acid (Correct):** Among all loop diuretics, ethacrynic acid is the **most ototoxic**. It is more likely to cause permanent deafness compared to Furosemide, which usually causes reversible hearing loss. * **Thiazides:** These act on the Distal Convoluted Tubule. Their primary side effects include hypokalemia, hyperuricemia, and hyperglycemia, but they do not possess ototoxic properties. * **Spironolactone:** A Potassium-sparing diuretic (Aldosterone antagonist). Its classic side effects are hyperkalemia and endocrine disruptions like gynecomastia. * **Triamterene:** A direct ENaC blocker (Potassium-sparing). It is associated with crystalluria and kidney stones but not deafness. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Loop Diuretic Side Effects (OH DANG!):** **O**totoxicity, **H**ypokalemia, **D**ehydration, **A**llergy (Sulfa), **N**ephritis (Interstitial), **G**out. * **Risk Factors:** Ototoxicity is potentiated when loop diuretics are co-administered with other ototoxic drugs like **Aminoglycosides** (e.g., Gentamicin), Cisplatin, or Vancomycin. * Ethacrynic acid is a **phenoxyacetic acid derivative**, making it the drug of choice for patients with a **Sulfa allergy** who require a loop diuretic.
Question 52: Which of the following diuretics results in the minimum net excretion of filtered sodium?
- A. Furosemide
- B. Thiazide
- C. Amiloride (Correct Answer)
- D. Acetazolamide
Explanation: The net excretion of filtered sodium depends on the site of action of the diuretic along the nephron and the percentage of sodium normally reabsorbed at that segment. **1. Why Amiloride is Correct:** Amiloride is a **Potassium-Sparing Diuretic** that acts on the late distal tubule and collecting duct by blocking ENaC (Epithelial Sodium Channels) [3]. Since approximately **only 1–3%** of filtered sodium reaches this segment, these drugs have the lowest natriuretic potency. They are primarily used to counteract potassium loss rather than for significant fluid removal. **2. Why the Other Options are Incorrect:** * **Furosemide (Loop Diuretic):** Acts on the Thick Ascending Limb (TAL) of the Loop of Henle, where **25–30%** of sodium is reabsorbed. It is the most potent diuretic ("High-ceiling"). * **Thiazides:** Act on the Distal Convoluted Tubule (DCT), where **5–10%** of sodium is reabsorbed [2]. They inhibit NaCl reabsorption by blocking the Na+/Cl- transporter (NCC) and have moderate natriuretic efficacy [2]. * **Acetazolamide (Carbonic Anhydrase Inhibitor):** Acts on the Proximal Convoluted Tubule (PCT), where **60–70%** of sodium is reabsorbed [1]. While it acts early, its net efficacy is lower than loop diuretics because distal segments compensate by reabsorbing the excess sodium load. However, it still results in more sodium excretion than amiloride. **Clinical Pearls for NEET-PG:** * **Potency Order:** Loop Diuretics > Thiazides > Acetazolamide > K+ Sparing Diuretics. * **Liddle’s Syndrome:** Amiloride is the treatment of choice (it blocks the overactive ENaC). * **Metabolic Side Effects:** Loop and Thiazide diuretics cause **Hypokalemic Metabolic Alkalosis**, whereas K+ sparing diuretics and Acetazolamide cause **Metabolic Acidosis** [1].
Question 53: What is the drug of choice for familial hyperkalemic periodic paralysis?
- A. acetazolamide (Correct Answer)
- B. rolofyline
- C. bumetanide
- D. torasemide
Explanation: **Explanation:** **Acetazolamide** is the drug of choice for both hypokalemic and hyperkalemic forms of **Familial Periodic Paralysis**. 1. **Mechanism of Action:** Acetazolamide is a Carbonic Anhydrase Inhibitor. In hyperkalemic periodic paralysis (caused by mutations in the SCN4A sodium channel), it works by inducing a mild **metabolic acidosis**. This increase in hydrogen ion concentration promotes the shift of potassium from the extracellular fluid into the cells and increases urinary potassium excretion, thereby stabilizing muscle cell membrane excitability and preventing paralytic attacks. **Analysis of Incorrect Options:** * **Rolofylline (B):** This is an adenosine A1 receptor antagonist. It was investigated for acute heart failure to preserve renal function but is not used in electrolyte-related muscle disorders. * **Bumetanide (C) & Torasemide (D):** These are high-efficacy **Loop Diuretics**. While they do increase potassium excretion, they are not the primary choice for periodic paralysis. In fact, loop diuretics are more specifically associated with treating hypervolemic states (edema, heart failure). **High-Yield Clinical Pearls for NEET-PG:** * **Other uses of Acetazolamide:** Glaucoma (decreases aqueous humor), Mountain sickness (prevents cerebral/pulmonary edema), and Urinary alkalinization (to excrete acidic drugs like aspirin). * **Side Effects:** Metabolic acidosis, hypokalemia, and paresthesia. It is contraindicated in patients with sulfonamide allergies. * **Hyperkalemic Periodic Paralysis:** Characterized by attacks of flaccid muscle weakness triggered by rest after exercise or potassium-rich foods.
Question 54: Carbonic anhydrase inhibitors lead to all of the following except?
- A. Loss of sodium and water
- B. Metabolic alkalosis (Correct Answer)
- C. Carbon dioxide retention
- D. Hypokalemia
Explanation: **Explanation:** Carbonic anhydrase inhibitors (CAIs), such as **Acetazolamide**, act primarily on the proximal convoluted tubule (PCT). They inhibit the enzyme carbonic anhydrase, which is essential for the reabsorption of sodium bicarbonate ($NaHCO_3$). **Why Metabolic Alkalosis is the correct answer:** CAIs prevent the reabsorption of bicarbonate, leading to significant **bicarbonate loss** in the urine (bicarbonaturia). The loss of this alkaline buffer results in **Hyperchloremic Metabolic Acidosis**, not alkalosis. Therefore, Option B is the "except" statement. **Analysis of Incorrect Options:** * **Option A (Loss of sodium and water):** By inhibiting $NaHCO_3$ reabsorption, CAIs increase the osmotic load in the tubule, leading to mild diuresis (natriuresis and water loss). * **Option C (Carbon dioxide retention):** Carbonic anhydrase is present in RBCs and is vital for converting $CO_2$ to bicarbonate for transport. Inhibition leads to decreased $CO_2$ excretion in the lungs and transient $CO_2$ retention in tissues. * **Option D (Hypokalemia):** Increased sodium delivery to the distal tubule enhances the $Na^+/K^+$ exchange, leading to increased potassium secretion and subsequent hypokalemia. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Acetazolamide is the DOC for **Acute Mountain Sickness** (it counteracts respiratory alkalosis) and **Open-angle Glaucoma** (decreases aqueous humor formation). * **Urinary pH:** CAIs make the urine **alkaline**, which can be used to increase the excretion of acidic drugs (e.g., aspirin) or prevent uric acid stones. * **Side Effects:** Drowsiness, paresthesia, and the formation of **calcium phosphate stones** (due to alkaline urine).
Question 55: Which one of the following is not an adverse effect of ACE inhibitors?
- A. Cough
- B. Hypokalemia (Correct Answer)
- C. Angioneurotic edema
- D. Skin rash
Explanation: **Explanation:** **Why Hypokalemia is the Correct Answer:** ACE inhibitors (ACEIs) block the conversion of Angiotensin I to Angiotensin II. Since Angiotensin II is a potent stimulator of **aldosterone** secretion from the adrenal cortex, its inhibition leads to decreased aldosterone levels. Aldosterone normally promotes sodium reabsorption and potassium excretion in the distal tubule; therefore, ACEIs cause potassium retention, leading to **Hyperkalemia**, not hypokalemia. This is a critical side effect, especially in patients with chronic kidney disease or those taking potassium-sparing diuretics. **Analysis of Incorrect Options:** * **A. Cough:** This is the most common side effect (approx. 10%). ACEIs prevent the breakdown of **bradykinin** and Substance P in the lungs, leading to their accumulation, which sensitizes cough receptors. * **C. Angioneurotic edema:** A rare but life-threatening side effect caused by the accumulation of bradykinin, leading to rapid swelling of the lips, tongue, and glottis. * **D. Skin rash:** Common with Captopril, often attributed to its sulfhydryl group, though it can occur with other ACEIs as well. **NEET-PG High-Yield Pearls:** * **Mnemonic for ACEI side effects (CAPTOPRIL):** **C**ough, **A**ngioedema, **P**roteinuria/ **P**otassium excess, **T**aste changes, **O**rthostatic hypotension, **P**regnancy (Teratogenic), **R**ash, **I**ncreased renin, **L**eukopenia. * **Teratogenicity:** ACEIs are contraindicated in pregnancy as they cause **fetal renal dysgenesis** and skull hypoplasia. * **Drug of Choice:** ACEIs are the first-line treatment for hypertension in patients with **Diabetes Mellitus** due to their renoprotective effects (reduction of efferent arteriolar resistance).
Question 56: All of the following drugs act as potassium-sparing diuretics, EXCEPT:
- A. Spironolactone
- B. Eplerenone
- C. Triamterene
- D. Thiazide (Correct Answer)
Explanation: **Explanation:** The correct answer is **D. Thiazide**. Thiazides (e.g., Hydrochlorothiazide) are **potassium-wasting** diuretics. They act on the Distal Convoluted Tubule (DCT) to inhibit the $Na^+/Cl^-$ symporter. This increases sodium delivery to the collecting ducts, where the exchange of $Na^+$ for $K^+$ (mediated by aldosterone) leads to increased urinary potassium excretion, potentially causing hypokalemia. **Analysis of Potassium-Sparing Diuretics (Incorrect Options):** Potassium-sparing diuretics act on the late DCT and collecting ducts to prevent $K^+$ secretion. They are divided into two classes: * **Aldosterone Antagonists (Options A & B):** **Spironolactone** and **Eplerenone** competitively block mineralocorticoid receptors. This prevents the synthesis of $Na^+/K^+$ ATPase pumps and epithelial sodium channels (ENaC), thereby retaining potassium. * **Direct ENaC Blockers (Option C):** **Triamterene** (and Amiloride) directly block the ENaC channels on the luminal membrane, independent of aldosterone. This decreases the electrical gradient that normally drives $K^+$ secretion into the urine. **Clinical Pearls for NEET-PG:** * **Liddle’s Syndrome:** Amiloride is the drug of choice. * **Spironolactone Side Effects:** It is non-specific and can cause **gynecomastia** and impotence in males due to anti-androgenic effects. **Eplerenone** is more selective and lacks these side effects. * **Drug of Choice for Conn’s Syndrome:** Spironolactone (Primary Hyperaldosteronism). * **Major Risk:** The most serious complication of all potassium-sparing diuretics is **hyperkalemia**, especially when combined with ACE inhibitors or ARBs.
Question 57: Which of the following is a potassium-sparing drug?
- A. Indapamide
- B. Frusemide
- C. Spironolactone (Correct Answer)
- D. Mannitol
Explanation: **Explanation:** **Correct Answer: C. Spironolactone** Spironolactone is a **Potassium-Sparing Diuretic** that acts as a competitive antagonist of the **Aldosterone receptor** (Mineralocorticoid Receptor) in the late distal tubule and collecting duct. By blocking aldosterone, it prevents the expression of ENaC (Epithelial Sodium Channels) and Na+/K+ ATPase pumps. This leads to the excretion of sodium and water while inhibiting the secretion of potassium into the tubular lumen, thereby "sparing" potassium. **Analysis of Incorrect Options:** * **A. Indapamide:** This is a **Thiazide-like diuretic**. It acts on the Distal Convoluted Tubule (DCT) by inhibiting the Na+/Cl- symporter. Like all thiazides, it causes hypokalemia. * **B. Frusemide:** This is a potent **Loop diuretic** that inhibits the Na+/K+/2Cl- co-transporter in the Thick Ascending Limb of the Henle’s loop. It is known for causing significant potassium loss (hypokalemia). * **C. Mannitol:** This is an **Osmotic diuretic**. It works by increasing the osmolarity of the tubular fluid, primarily in the Proximal Convoluted Tubule and the descending limb of the Loop of Henle. **High-Yield Clinical Pearls for NEET-PG:** * **Classification:** Potassium-sparing diuretics are divided into **Aldosterone Antagonists** (Spironolactone, Eplerenone) and **Direct ENaC Blockers** (Amiloride, Triamterene). * **Side Effects:** Spironolactone can cause **gynecomastia** and impotence due to its non-specific anti-androgenic effects. **Eplerenone** is a more selective alternative with fewer hormonal side effects. * **Clinical Use:** Spironolactone is the drug of choice for **Primary Hyperaldosteronism (Conn’s Syndrome)** and is proven to reduce mortality in **Congestive Heart Failure (NYHA Class III/IV)**. * **Contraindication:** Avoid using these drugs with ACE inhibitors or ARBs as the combination significantly increases the risk of life-threatening **hyperkalemia**.
Question 58: Which of the following are potassium-sparing diuretics?
- A. Spironolactone
- B. Triamterene
- C. Amiloride
- D. All of the above (Correct Answer)
Explanation: **Explanation:** Potassium-sparing diuretics are a class of drugs that act on the **late distal tubule and collecting duct** of the nephron. Unlike loop or thiazide diuretics, they increase sodium excretion without causing a concomitant loss of potassium in the urine. The correct answer is **D (All of the above)** because these drugs represent the two distinct sub-classes of potassium-sparing diuretics: 1. **Aldosterone Antagonists (Spironolactone):** This drug competitively inhibits the Mineralocorticoid Receptor (MR). By blocking aldosterone, it prevents the synthesis of Na+/K+ ATPase pumps and ENaC channels, thereby reducing sodium reabsorption and potassium secretion. 2. **Renal Epithelial Sodium Channel (ENaC) Blockers (Amiloride and Triamterene):** These drugs directly block the ENaC channels on the luminal membrane of principal cells. By preventing sodium entry into the cell, they decrease the electrical gradient that normally drives potassium secretion into the tubular lumen. **Clinical Pearls for NEET-PG:** * **Site of Action:** Late distal tubule and cortical collecting duct. * **Primary Side Effect:** **Hyperkalemia** (especially when used with ACE inhibitors or in patients with renal impairment). * **Spironolactone Specifics:** It is a non-specific steroid antagonist and can cause **gynecomastia** and impotence in men due to its anti-androgenic effects. **Eplerenone** is a more selective alternative with fewer hormonal side effects. * **Liddle’s Syndrome:** Amiloride is the drug of choice for this rare genetic condition. * **Lithium-Induced Diabetes Insipidus:** Amiloride is used to block lithium entry through ENaC channels in the collecting duct.
Question 59: Which of the following is true about acetazolamide?
- A. Increases sodium reabsorption and potassium secretion
- B. Is a carbonic anhydrase inhibitor (Correct Answer)
- C. Acts at the ascending limb of the loop of Henle
- D. Increases aqueous outflow mainly
Explanation: **Explanation:** **Acetazolamide** is the prototype of **Carbonic Anhydrase Inhibitors (CAIs)**. It works by reversibly inhibiting the enzyme carbonic anhydrase (both cytoplasmic type II and membrane-bound type IV) in the **Proximal Convoluted Tubule (PCT)**. This inhibition prevents the dehydration of $H_2CO_3$ and the reabsorption of $NaHCO_3$, leading to alkaline diuresis. **Analysis of Options:** * **Option B (Correct):** Its primary mechanism is the inhibition of carbonic anhydrase, which reduces $H^+$ availability for the $Na^+/H^+$ exchanger, leading to increased excretion of sodium, potassium, and bicarbonate. * **Option A (Incorrect):** Acetazolamide **decreases** sodium reabsorption and **increases** potassium secretion (due to increased distal delivery of sodium). * **Option C (Incorrect):** It acts primarily at the **Proximal Convoluted Tubule (PCT)**, not the ascending limb of the loop of Henle (which is the site for Loop Diuretics like Furosemide). * **Option D (Incorrect):** In glaucoma, acetazolamide works by **decreasing the production** of aqueous humor (by inhibiting CA in the ciliary body), not by increasing its outflow. **High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic Uses:** Glaucoma (decreases aqueous production), Acute Mountain Sickness (counteracts respiratory alkalosis), Urinary Alkalinization (to excrete acidic drugs like uric acid/cystine), and Periodic Paralysis. * **Adverse Effects:** Metabolic acidosis (Hyperchloremic), Hypokalemia, Paresthesia, and Renal stones (due to calcium phosphate precipitation in alkaline urine). * **Contraindication:** Avoid in Hepatic Cirrhosis, as it decreases ammonia excretion, potentially precipitating hepatic encephalopathy.
Question 60: Which of the following is a false statement regarding thiazide diuretics?
- A. Used in congestive heart failure
- B. Causes hyperglycemia
- C. Increases uric acid concentration in serum
- D. Increases calcium excretion in urine (Correct Answer)
Explanation: ### Explanation The correct answer is **D (Increases calcium excretion in urine)** because this statement is false. Thiazide diuretics actually **decrease** calcium excretion (causing hypercalcemia and hypocalciuria). #### Why Option D is False (The Mechanism) Thiazides inhibit the **Na⁺-Cl⁻ symporter** in the Distal Convoluted Tubule (DCT). By blocking sodium entry, the intracellular concentration of Na⁺ drops. This enhances the activity of the basolateral **Na⁺/Ca²⁺ exchanger**, which pumps more Na⁺ into the cell and more Ca²⁺ into the blood. Consequently, more calcium is reabsorbed from the tubular lumen, leading to **hypocalciuria**. This makes thiazides useful in preventing calcium oxalate kidney stones. #### Analysis of Other Options * **A. Used in CHF:** True. Thiazides are used to manage edema in mild-to-moderate congestive heart failure, though Loop diuretics are preferred for acute or severe cases. * **B. Causes hyperglycemia:** True. Thiazides inhibit insulin release from the pancreas (due to K⁺ depletion) and decrease peripheral glucose utilization, potentially worsening diabetes. * **C. Increases uric acid:** True. Thiazides compete with uric acid for the organic acid secretory pump in the proximal tubule, leading to **hyperuricemia**, which can precipitate gout. #### NEET-PG High-Yield Pearls * **Mnemonic for Thiazide Side Effects (Hyper-GLUC):** **G**lycemia, **L**ipidemia (increased LDL/TG), **U**ricemia, and **C**alcemia. * **Electrolyte Profile:** Thiazides cause **Hypo**kalemia, **Hypo**natremia, **Hypo**magnesemia, but **Hyper**calcemia. * **Clinical Use:** They are the first-line antihypertensive for elderly and African-American patients. * **Paradoxical Use:** Thiazides are used to treat **Nephrogenic Diabetes Insipidus** because they induce mild volume depletion, triggering compensatory salt and water reabsorption in the proximal tubule.
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
Practice Questions
Diuretics in Renal Disorders
Practice Questions
Adverse Effects and Drug Interactions
Practice Questions
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