Diuretics Practice Questions

Q: Which drug causes deafness?

Ethacrynic acid. **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.

Q: Which of the following diuretics results in the minimum net excretion of filtered sodium?

Amiloride. 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].

Q: What is the drug of choice for familial hyperkalemic periodic paralysis?

acetazolamide. **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.

Q: Carbonic anhydrase inhibitors lead to all of the following except?

Metabolic alkalosis. **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).

Q: Which drug is recommended for chemoprophylaxis one day before induction into high altitude areas?

Acetazolamide. **Explanation:** **Acetazolamide** is the drug of choice for the prevention of **Acute Mountain Sickness (AMS)**. It is a carbonic anhydrase inhibitor that works by inhibiting the enzyme in the proximal convoluted tubule of the kidney. This leads to bicarbonate diuresis, resulting in a mild **metabolic acidosis**. To compensate for this acidosis, the body increases the respiratory rate (hyperventilation), which improves oxygenation and accelerates the natural process of acclimatization. For effective prophylaxis, it is recommended to start the drug 24 hours before ascent. **Analysis of Incorrect Options:** * **Furosemide (Option B):** While it is a potent loop diuretic, it is used in the *treatment* of High-Altitude Pulmonary Edema (HAPE) to reduce fluid in the lungs, but it is not used for routine prophylaxis of AMS. * **Doxycycline (Option C):** This is an antibiotic used for chemoprophylaxis against Malaria or Leptospirosis, having no role in high-altitude illness. * **Paracetamol (Option D):** This is an analgesic used to treat the headache associated with altitude sickness but does not prevent the underlying physiological cause or aid in acclimatization. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Induces metabolic acidosis → stimulates chemoreceptors → increases minute ventilation. * **Side Effects:** Common side effects include **paresthesia** (tingling in fingers/toes) and a **metallic taste** when consuming carbonated beverages. * **Contraindication:** Avoid in patients with a known **Sulfa allergy**. * **Treatment of Choice:** For established HAPE, the drug of choice is **Nifedipine**; for High-Altitude Cerebral Edema (HACE), it is **Dexamethasone**.

Q: Which of the following is a potassium-sparing drug?

Spironolactone. **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**.

Q: Which of the following is a false statement regarding thiazide diuretics?

Increases calcium excretion in urine. ### 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.

Q: At equally natriuretic doses, which of the following drugs causes maximum potassium excretion?

Acetazolamide. **Explanation:** The correct answer is **Acetazolamide**. **1. Why Acetazolamide is correct:** Acetazolamide is a Carbonic Anhydrase Inhibitor (CAI) that acts on the proximal convoluted tubule (PCT). It inhibits the reabsorption of sodium bicarbonate ($NaHCO_3$). This results in a large delivery of sodium and non-reabsorbable bicarbonate ions to the distal segments of the nephron. To compensate for the high sodium load, the distal tubule and collecting ducts exchange sodium for potassium. Furthermore, the presence of bicarbonate (a negative anion) in the distal tubule creates a negative luminal potential that further "pulls" $K^+$ out of the cells. Consequently, at doses that produce the same level of natriuresis as other diuretics, CAIs cause the **highest magnitude of potassium loss.** **2. Why the other options are incorrect:** * **Spironolactone:** This is a potassium-sparing diuretic. It antagonizes aldosterone receptors, leading to potassium retention rather than excretion. * **Furosemide:** While loop diuretics cause significant hypokalemia, their primary site of action is the Thick Ascending Limb. At *equally natriuretic doses*, the distal delivery of bicarbonate seen with CAIs makes Acetazolamide more potent at inducing kaliuresis. * **Aldosterone:** This is a mineralocorticoid, not a diuretic. While it increases $K^+$ excretion, it causes sodium *retention* (edema), making it the opposite of a natriuretic agent. **3. NEET-PG High-Yield Pearls:** * **Site of Action:** Acetazolamide (PCT), Furosemide (TAL of Loop of Henle), Thiazides (DCT). * **Metabolic Effect:** Acetazolamide causes **Hyperchloremic Metabolic Acidosis** (due to $HCO_3$ loss), whereas Loop and Thiazide diuretics cause **Metabolic Alkalosis**. * **Clinical Use:** Acetazolamide is the drug of choice for Glaucoma and Mountain Sickness, but it is a weak diuretic due to compensatory reabsorption in distal segments.

Q: Spironolactone is least commonly used in which of the following conditions?

Hypertension. The correct answer is **Hypertension**. While Spironolactone is a diuretic, it is considered a **weak diuretic** when used alone because it acts on the late distal tubule and collecting duct, where only about 2–3% of sodium reabsorption occurs [1]. In the management of essential hypertension, Thiazides or Calcium Channel Blockers are preferred as first-line agents. Spironolactone is typically reserved for resistant hypertension or specific cases where hyperaldosteronism is a contributing factor. **Why other options are incorrect:** * **Congestive Heart Failure (CHF):** Spironolactone is a cornerstone therapy (RALES trial). It prevents myocardial remodeling and fibrosis caused by aldosterone, significantly reducing mortality in patients with NYHA Class II-IV heart failure. * **Cirrhotic Edema:** It is the **drug of choice** for edema and ascites in liver cirrhosis. In cirrhosis, there is secondary hyperaldosteronism due to decreased hepatic clearance of aldosterone; Spironolactone directly antagonizes this effect [2]. * **Primary Hyperaldosteronism (Conn’s Syndrome):** It is used as the primary medical treatment to block the effects of excessive aldosterone secretion [1, 3], especially in patients who are not candidates for surgery. **NEET-PG High-Yield Pearls:** * **Mechanism:** Competitive antagonist at the Mineralocorticoid Receptor (MR) in the cortical collecting duct [1, 2, 3]. * **Side Effects:** Hyperkalemia (most common) [1, 3] and **Gynecomastia** (due to non-specific binding to androgen and progesterone receptors) [2]. * **Eplerenone:** A more selective mineralocorticoid antagonist with fewer endocrine side effects (no gynecomastia) [2]. * **Contraindication:** Should not be used if serum potassium is >5.0 mEq/L or in severe renal impairment (CrCl <30 mL/min) [1, 3].

Q: Which of the following medications is contraindicated in patients with allergy to sulfonamides?

Brinzolamide. **Explanation:** **Brinzolamide** is a topical Carbonic Anhydrase Inhibitor (CAI) used to reduce intraocular pressure in glaucoma. Chemically, CAIs (including Brinzolamide and Dorzolamide) are **sulfonamide derivatives**. Although administered topically, they undergo systemic absorption. In patients with a known sulfonamide allergy, these drugs can trigger hypersensitivity reactions ranging from mild skin rashes to severe conditions like Stevens-Johnson Syndrome. Therefore, a history of sulfa allergy is a contraindication for their use. **Analysis of Incorrect Options:** * **A. Levobunolol:** This is a non-selective **beta-blocker**. It is contraindicated in patients with asthma, COPD, or bradycardia, but it does not share cross-reactivity with sulfonamides. * **B. Bimatoprost:** This is a **prostaglandin analogue**. Its primary side effects include iris repigmentation, hypertrichosis of lashes, and cystoid macular edema, but it is safe for sulfa-allergic patients. * **C. Brimonidine:** This is a highly selective **alpha-2 adrenergic agonist**. While it frequently causes local follicular conjunctivitis (allergic reaction), it is not a sulfonamide. **High-Yield NEET-PG Pearls:** * **Topical CAIs:** Brinzolamide (suspension, less stinging) and Dorzolamide (solution, more stinging). * **Systemic CAI:** Acetazolamide (Diamox) is also a sulfonamide and carries the same contraindication. * **Mechanism:** CAIs reduce IOP by inhibiting carbonic anhydrase in the ciliary epithelium, thereby decreasing aqueous humor production. * **Cross-Reactivity Rule:** Always screen for sulfa allergy before prescribing CAIs, loop diuretics (Furosemide), or thiazides.

Question 1

Which drug causes deafness?

Accepted Answer

Ethacrynic acid

Answer

Thiazide

Answer

Spironolactone

Answer

Triamterene

Question 2

Which of the following diuretics results in the minimum net excretion of filtered sodium?

Accepted Answer

Amiloride

Answer

Furosemide

Answer

Thiazide

Answer

Acetazolamide

Question 3

What is the drug of choice for familial hyperkalemic periodic paralysis?

Accepted Answer

acetazolamide

Answer

rolofyline

Answer

bumetanide

Answer

torasemide

Question 4

Carbonic anhydrase inhibitors lead to all of the following except?

Accepted Answer

Metabolic alkalosis

Answer

Loss of sodium and water

Answer

Carbon dioxide retention

Answer

Hypokalemia

Question 5

Which drug is recommended for chemoprophylaxis one day before induction into high altitude areas?

Accepted Answer

Acetazolamide

Answer

Furosemide

Answer

Doxycycline

Answer

Paracetamol

Question 6

Which of the following is a potassium-sparing drug?

Accepted Answer

Spironolactone

Answer

Indapamide

Answer

Frusemide

Answer

Mannitol

Question 7

Which of the following is a false statement regarding thiazide diuretics?

Accepted Answer

Increases calcium excretion in urine

Answer

Used in congestive heart failure

Answer

Causes hyperglycemia

Answer

Increases uric acid concentration in serum

Question 8

At equally natriuretic doses, which of the following drugs causes maximum potassium excretion?

Accepted Answer

Acetazolamide

Answer

Spironolactone

Answer

Furosemide

Answer

Aldosterone

Question 9

Spironolactone is least commonly used in which of the following conditions?

Accepted Answer

Hypertension

Answer

Congestive heart failure

Answer

Cirrhotic edema

Answer

Primary hyperaldosteronism

Question 10

Which of the following medications is contraindicated in patients with allergy to sulfonamides?

Accepted Answer

Brinzolamide

Answer

Levobunolol

Answer

Bimatoprost

Answer

Brimonidine

Diuretics — MCQs

Diuretics — MCQs

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