Diuretics — MCQs

Diuretics Indian Medical PG Practice Questions and MCQs

Question 81: Which of the following metabolic abnormalities is seen with long-term use of spironolactone?

A. Metabolic acidosis (Correct Answer)
B. Metabolic alkalosis
C. Hyperkalemia
D. None of the above

Explanation: **Explanation:** Spironolactone is a potassium-sparing diuretic that acts as a competitive antagonist of the mineralocorticoid receptor in the late distal tubule and collecting duct. **Why Metabolic Acidosis is Correct:** Aldosterone normally promotes the reabsorption of sodium ($Na^+$) in exchange for the secretion of potassium ($K^+$) and hydrogen ions ($H^+$) via the $H^+$-ATPase pump in the intercalated cells. By inhibiting aldosterone, spironolactone reduces the secretion of $H^+$ into the tubular lumen. This retention of hydrogen ions in the blood leads to **Hyperchloremic Metabolic Acidosis** (specifically a Normal Anion Gap Metabolic Acidosis). **Analysis of Incorrect Options:** * **B. Metabolic Alkalosis:** This is typically seen with "Loop" and "Thiazide" diuretics. These drugs increase sodium delivery to the distal tubule, stimulating $H^+$ secretion and causing contraction alkalosis. * **C. Hyperkalemia:** While spironolactone **does** cause hyperkalemia (by inhibiting $K^+$ secretion), the question specifically asks for the **metabolic** (acid-base) abnormality. Hyperkalemia is an electrolyte abnormality, not a metabolic one. In the context of acid-base balance, hyperkalemia and metabolic acidosis often coexist. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Spironolactone causes **"High K and Low pH"** (Hyperkalemia and Acidosis). * **Side Effects:** Beyond metabolic changes, it causes **gynecomastia** and impotence in men due to its non-specific anti-androgenic effects (Eplerenone is a more selective alternative). * **Drug of Choice:** It is the DOC for edema in **Cirrhosis** and for treating **Primary Hyperaldosteronism (Conn’s Syndrome)**. * **Mortality Benefit:** It is proven to reduce mortality in patients with Chronic Heart Failure (NYHA Class II-IV).

Question 82: Spironolactone is most useful in?

A. Cardiac hypertrophy
B. Cirrhotic ascites (Correct Answer)
C. Exudative pleural effusion
D. Renal artery stenosis

Explanation: **Explanation:** **Spironolactone** is a potassium-sparing diuretic that acts as a competitive antagonist to the **Aldosterone receptor** (Mineralocorticoid receptor) in the distal convoluted tubule and collecting duct. **Why Cirrhotic Ascites is the correct answer:** In patients with liver cirrhosis, there is significant activation of the Renin-Angiotensin-Aldosterone System (RAAS) due to peripheral vasodilation and decreased effective arterial blood volume. This leads to **Secondary Hyperaldosteronism**, causing massive sodium and water retention. Spironolactone is the **drug of choice** for cirrhotic ascites because it directly counteracts the high levels of circulating aldosterone, promoting natriuresis while preserving potassium. **Analysis of Incorrect Options:** * **Cardiac Hypertrophy:** While Spironolactone (and Eplerenone) reduces cardiac remodeling and mortality in chronic heart failure (RALES trial), it is used as an adjunct. It is not the "most useful" or primary indication compared to its definitive role in managing the pathophysiology of ascites. * **Exudative Pleural Effusion:** This is typically caused by inflammation or malignancy. Diuretics are used for *transudative* effusions (like those in heart failure); they have no role in treating the underlying cause of exudative fluid. * **Renal Artery Stenosis:** This condition causes high renin levels. However, using Spironolactone or ACE inhibitors in bilateral renal artery stenosis can lead to a dangerous drop in GFR and acute kidney injury. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Spironolactone is the DOC for **Cirrhotic Ascites** and **Conn’s Syndrome** (Primary Hyperaldosteronism). * **Mechanism:** Inhibits the expression of ENaC (Epithelial Sodium Channels) and Na+/K+ ATPase. * **Side Effects:** The most characteristic side effect is **Gynecomastia** (due to non-specific binding to androgen and progesterone receptors). Eplerenone is a more selective alternative without this side effect. * **Metabolite:** **Canrenone** is the active metabolite of Spironolactone.

Question 83: Which of the following statements about furosemide is true?

A. It is administered only by the intravenous route.
B. It causes mild diuresis.
C. It is used in the management of pulmonary edema. (Correct Answer)
D. It acts on the proximal convoluted tubule (PCT).

Explanation: ### Explanation **Correct Answer: C. It is used in the management of pulmonary edema.** **Mechanism and Rationale:** Furosemide is a potent **Loop Diuretic** that inhibits the **Na⁺-K⁺-2Cl⁻ symporter** in the Thick Ascending Limb (TAL) of the Loop of Henle. It is the drug of choice for acute pulmonary edema because of two distinct actions: 1. **Hemodynamic effect:** When given intravenously, it causes rapid **venodilation** (mediated by prostaglandins), which reduces venous return (preload) even before the diuretic effect begins. 2. **Diuretic effect:** It promotes the excretion of sodium and water, reducing the overall fluid overload. --- ### Why other options are incorrect: * **Option A:** Furosemide has good oral bioavailability (~60%) and is commonly used in tablet form for chronic heart failure and hypertension. It is administered both **orally and intravenously**. * **Option B:** It is a **"High-ceiling" diuretic**, meaning it causes massive, brisk diuresis. It is the most efficacious class of diuretics, not "mild." * **Option D:** It acts on the **Thick Ascending Limb (TAL)** of the Loop of Henle, not the PCT. Acetazolamide is an example of a drug acting on the PCT. --- ### NEET-PG High-Yield Pearls: * **Side Effects (OH DANG!):** **O**totoxicity (especially with aminoglycosides), **H**ypokalemia, **D**ehydration, **A**llergy (Sulfa drug), **N**ephritis (Interstitial), **G**out (Hyperuricemia). * **Electrolyte Changes:** It causes **Hypomagnesemia** and **Hypocalcemia** (Loop diuretics "lose" calcium, whereas Thiazides "thrive" on/retain calcium). * **Drug Interaction:** NSAIDs can reduce the diuretic efficacy of furosemide by inhibiting prostaglandin synthesis.

Question 84: Spironolactone is most effective for which type of edema?

A. Cirrhotic edema (Correct Answer)
B. Cardiac edema
C. Idiopathic edema
D. Nutritional edema

Explanation: **Explanation:** **1. Why Cirrhotic Edema is Correct:** Spironolactone is the **drug of choice** for edema associated with liver cirrhosis. In cirrhosis, there is decreased hepatic clearance of aldosterone and activation of the Renin-Angiotensin-Aldosterone System (RAAS) due to splanchnic vasodilation. This leads to **secondary hyperaldosteronism**, causing significant sodium and water retention. As a competitive antagonist of the Mineralocorticoid Receptor (MR), spironolactone directly counteracts this excess aldosterone, making it more effective here than in other types of edema. **2. Why Other Options are Incorrect:** * **Cardiac Edema:** While spironolactone is used in Heart Failure (HF) to reduce mortality and remodeling (RALES trial), the primary diuretics for acute symptomatic relief of cardiac edema are **Loop diuretics** (e.g., Furosemide) due to their high efficacy and rapid onset. * **Idiopathic Edema:** This is typically managed with weight reduction, salt restriction, or occasionally low-dose thiazides. Spironolactone is not the primary treatment. * **Nutritional Edema:** This is primarily due to hypoproteinemia (low oncotic pressure). Treatment focuses on protein supplementation and addressing the underlying deficiency rather than specific hormonal antagonism. **3. Clinical Pearls for NEET-PG:** * **Mechanism:** Competitive antagonist of aldosterone at the late distal tubule and collecting duct. * **Side Effects:** The most high-yield side effect is **Gynecomastia** (due to non-specific binding to androgen receptors). Eplerenone is a more selective alternative that avoids this. * **Electrolyte Shift:** Always monitor for **Hyperkalemia**, especially if the patient is also on ACE inhibitors. * **Paradoxical Use:** It is also used in **Conn’s Syndrome** (Primary hyperaldosteronism) and Polycystic Ovary Syndrome (PCOS) for its anti-androgenic effects.

Question 85: Mannitol is not useful for which of the following conditions?

A. Glaucoma
B. Raised intracranial tension
C. Impending renal failure
D. Pulmonary edema (Correct Answer)

Explanation: **Explanation:** **Mannitol** is a prototype osmotic diuretic. It works by increasing the osmolarity of the plasma and tubular fluid, drawing water out of the intracellular and interstitial compartments into the vascular space. **Why it is NOT used in Pulmonary Edema (Option D):** Mannitol initially causes a rapid expansion of extracellular fluid (ECF) volume as it pulls water from cells into the bloodstream. In patients with cardiac insufficiency or pulmonary congestion, this sudden increase in preload can worsen **pulmonary edema** and potentially precipitate acute heart failure. Therefore, pulmonary edema is a strict **contraindication** for mannitol. **Analysis of Incorrect Options:** * **A. Glaucoma:** Mannitol increases plasma osmolarity, creating an osmotic gradient that draws aqueous humor from the eye into the systemic circulation, thereby acutely reducing intraocular pressure. * **B. Raised Intracranial Tension (ICT):** This is the most common clinical use. Mannitol draws fluid out of the brain parenchyma into the vascular space, effectively reducing cerebral edema. * **C. Impending Renal Failure:** In conditions like shock or hemolysis, mannitol maintains urine flow by preventing water reabsorption in the proximal tubule and Loop of Henle, helping to "flush" out toxins and prevent tubular necrosis. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Action:** Primarily the Thin Descending Limb of the Loop of Henle (and Proximal Convoluted Tubule). * **Route:** Must be given **IV only** (not absorbed orally; causes osmotic diarrhea if ingested). * **Contraindications:** Acute pulmonary edema, severe congestive heart failure, and established anuria (chronic renal failure). * **Side Effect:** Headache is common due to the stretching of dural vessels.

Question 86: Which of the following is NOT caused by thiazide diuretics?

A. Hyperuricemia
B. Ototoxicity (Correct Answer)
C. Hypercalcemia
D. Hypokalemia

Explanation: Thiazide diuretics (e.g., Hydrochlorothiazide, Chlorthalidone) act on the distal convoluted tubule (DCT) by inhibiting the **Na⁺-Cl⁻ symporter**. **Why Ototoxicity is the Correct Answer:** Ototoxicity is a classic side effect of **Loop diuretics** (like Furosemide and Ethacrynic acid), not Thiazides. Loop diuretics inhibit the Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending limb of Henle; a similar transporter exists in the stria vascularis of the inner ear. Disruption of this transporter leads to electrolyte imbalances in the endolymph, causing tinnitus or hearing loss. Thiazides do not affect this mechanism. **Explanation of Incorrect Options:** * **Hyperuricemia:** Thiazides compete with uric acid for the organic acid secretory pump in the proximal tubule. This leads to decreased uric acid excretion, potentially precipitating gout. * **Hypercalcemia:** Unlike Loop diuretics (which cause hypocalcemia), Thiazides **increase** calcium reabsorption in the DCT. This occurs because the inhibition of Na⁺ entry increases the activity of the Na⁺/Ca²⁺ exchanger on the basolateral membrane. * **Hypokalemia:** By increasing sodium delivery to the late distal tubule and collecting duct, Thiazides stimulate the exchange of Na⁺ for K⁺ (mediated by aldosterone), leading to potassium depletion. **High-Yield NEET-PG Pearls:** * **Mnemonic for Thiazide side effects:** "Hyper **GLUC**" — Hyper**G**lycemia, Hyper**L**ipidemia, Hyper**U**ricemia, Hyper**C**alcemia. * **Clinical Use:** Because they cause hypercalcemia, Thiazides are the diuretic of choice for hypertensive patients with **osteoporosis** or **recurrent calcium oxalate stones** (as they reduce urinary calcium). * **Chlorthalidone** is often preferred over Hydrochlorothiazide due to its longer half-life and superior evidence in reducing cardiovascular events.

Question 87: Which of the following adverse effects is NOT typically produced by thiazide diuretics?

A. Hyperglycemia
B. Hyperkalemia (Correct Answer)
C. Hypokalemia
D. Hyperlipidemia

Explanation: **Explanation:** Thiazide diuretics (e.g., Hydrochlorothiazide, Chlorthalidone) act on the **Distal Convoluted Tubule (DCT)** by inhibiting the $Na^+/Cl^-$ symporter. The correct answer is **Hyperkalemia** because Thiazides characteristically cause **Hypokalemia**, not hyperkalemia. **1. Why Hyperkalemia is the correct answer (The Mechanism):** Thiazides increase sodium delivery to the late distal tubule and collecting duct. To reabsorb this excess sodium, the body activates the $Na^+/K^+$ exchange mechanism (driven by Aldosterone), leading to increased secretion of Potassium ($K^+$) into the urine. This results in **Hypokalemia**. Hyperkalemia is typically associated with Potassium-sparing diuretics (e.g., Spironolactone) or ACE inhibitors. **2. Analysis of Incorrect Options:** * **Hyperglycemia:** Thiazides inhibit insulin release from the pancreas (due to low $K^+$ levels) and decrease peripheral glucose utilization, leading to elevated blood sugar. * **Hypokalemia:** As explained above, this is a hallmark side effect due to increased $K^+$ excretion in the distal nephron. * **Hyperlipidemia:** Thiazides can cause a transient increase in serum LDL cholesterol and triglycerides. **Clinical Pearls for NEET-PG:** * **The "HYPER" Mnemonic:** Thiazides cause **Hyper**glycemia, **Hyper**lipidemia, **Hyper**uricemia (can precipitate Gout), and **Hyper**calcemia (useful in preventing calcium stones). * **The "HYPO" Mnemonic:** They cause **Hypo**kalemia, **Hypo**magnesemia, and **Hypo**natremia. * **Drug of Choice:** Chlorthalidone is often preferred over Hydrochlorothiazide due to its longer half-life and better evidence in reducing cardiovascular events.

Question 88: Which diuretic is commonly used in the management of essential hypertension?

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

Explanation: **Explanation:** **Hydrochlorothiazide (Option A)** is the correct answer because **Thiazide diuretics** are the first-line diuretic agents for the management of essential hypertension. Their antihypertensive effect occurs in two phases: initially, they reduce blood pressure by decreasing blood volume and cardiac output; long-term, they act as direct vasodilators by reducing intracellular sodium in vascular smooth muscle, which decreases peripheral vascular resistance. **Why other options are incorrect:** * **Amiloride (Option B):** This is a potassium-sparing diuretic. It has weak antihypertensive efficacy when used alone and is primarily used in combination with Thiazides to prevent hypokalemia. * **Furosemide (Option C):** A loop diuretic with a short duration of action (4–6 hours). While potent, it is less effective than Thiazides for essential hypertension unless the patient has concomitant chronic kidney disease (CrCl <30 ml/min) or congestive heart failure. * **Acetazolamide (Option D):** A carbonic anhydrase inhibitor used mainly for glaucoma, altitude sickness, and urinary alkalinization. It is not used for hypertension due to its weak diuretic effect and risk of metabolic acidosis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Chlorthalidone** is often preferred over Hydrochlorothiazide in recent guidelines due to its longer half-life and superior evidence in reducing cardiovascular events. 2. **Metabolic Side Effects of Thiazides:** Remember the "4 Hypers and 2 Hypos": **Hyper**glycemia, **Hyper**lipidemia, **Hyper**uricemia, **Hyper**calcemia; **Hypo**kalemia and **Hypo**natremia. 3. Thiazides are ineffective if the GFR is less than 30 ml/min (except **Metolazone**).

Question 89: All of the following are true regarding diuretic-associated hypokalemia, EXCEPT:

A. Loop diuretics cause more hypokalemia than thiazide diuretics. (Correct Answer)
B. Increased distal tubular sodium delivery and distal tubular flow rate result in hypokalemia.
C. Secondary hyperaldosteronism also plays a role.
D. Thiazides cause hypocalciuria.

Explanation: ### Explanation **1. Why Option A is the Correct Answer (The False Statement):** Contrary to common belief, **Thiazide diuretics cause more clinically significant hypokalemia than Loop diuretics.** While Loop diuretics are more potent "natriuretics" (excreting more sodium), they have a shorter duration of action. Thiazides have a longer half-life, leading to a sustained increase in sodium delivery to the distal tubule over a longer period. This prolonged exposure results in a greater cumulative loss of potassium. **2. Analysis of Other Options:** * **Option B (Correct Mechanism):** Diuretics inhibit sodium reabsorption upstream (Loop of Henle or Distal Tubule). This increases **distal sodium delivery**. When more sodium reaches the collecting duct, it is reabsorbed via ENaC channels in exchange for potassium secretion (mediated by ROMK channels), leading to hypokalemia. * **Option C (Correct Mechanism):** Diuretics cause volume depletion, which activates the **Renin-Angiotensin-Aldosterone System (RAAS)**. Secondary hyperaldosteronism further stimulates the principal cells to reabsorb sodium and excrete potassium and hydrogen ions. * **Option D (True Statement):** Thiazides increase calcium reabsorption in the distal convoluted tubule, leading to **hypocalciuria**. This makes them useful in preventing calcium oxalate kidney stones. In contrast, Loop diuretics cause hypercalciuria ("Loops lose calcium"). **3. High-Yield Clinical Pearls for NEET-PG:** * **Metabolic Profile:** Both Thiazides and Loops cause **Hypokalemic Metabolic Alkalosis**. * **Calcium Rule:** Thiazides = Hypercalcemia/Hypocalciuria; Loops = Hypocalcemia/Hypercalciuria. * **Drug of Choice:** Thiazides are preferred for hypertension; Loops are preferred for edematous states (CHF, Cirrhosis). * **Digoxin Toxicity:** Diuretic-induced hypokalemia is a major risk factor for precipitating digoxin toxicity.

Question 90: Which of the following medications can be used to treat hypercalciuria?

A. Torsemide
B. Acetazolamide
C. Frusemide
D. Indapamide (Correct Answer)

Explanation: ### Explanation The correct answer is **Indapamide (Option D)**. **Why Indapamide is correct:** Indapamide is a **thiazide-like diuretic** [1]. Thiazides and thiazide-like diuretics (e.g., Chlorthalidone, Metolazone) act on the Distal Convoluted Tubule (DCT) by inhibiting the $Na^+/Cl^-$ symporter [1], [2]. This action leads to a decrease in intracellular sodium, which enhances the activity of the $Na^+/Ca^{2+}$ exchanger on the basolateral membrane. Consequently, more calcium is reabsorbed from the tubular fluid into the blood [1], [2]. By **decreasing urinary calcium excretion (hypocalciuria)**, these drugs are the treatment of choice for idiopathic hypercalciuria and the prevention of calcium oxalate renal stones [1], [2]. **Why other options are incorrect:** * **Torsemide & Frusemide (Options A & C):** These are **Loop Diuretics**. They inhibit the $Na^+/K^+/2Cl^-$ cotransporter in the Thick Ascending Limb (TAL). This abolishes the lumen-positive potential required for the paracellular reabsorption of divalent cations. Therefore, loop diuretics **increase calcium excretion** ("Loops Lose Calcium") [1] and are used to treat hypercalcemia, not hypercalciuria. * **Acetazolamide (Option B):** This is a Carbonic Anhydrase inhibitor. It acts on the Proximal Convoluted Tubule and increases the excretion of bicarbonate, which can lead to alkaline urine. This actually **increases the risk of calcium phosphate stone formation** and is not used for hypercalciuria [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **L**oops **L**ose calcium; **T**hiazides **T**ake (retain) calcium. * **Paradoxical use:** Thiazides are used in **Nephrogenic Diabetes Insipidus** to reduce polyuria. * **Metabolic side effects of Thiazides:** Hyper**G**lycemia, Hyper**L**ipidemia, Hyper**U**ricemia, and Hyper**C**alcemia (Mnemonic: **GLUC**) [1]. * Indapamide is often preferred in hypertensive patients with renal impairment as it is primarily excreted via the biliary route [1].

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Carbonic Anhydrase Inhibitors

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Loop Diuretics

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Thiazide and Thiazide-Like Diuretics

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Potassium-Sparing Diuretics

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Carbonic Anhydrase Inhibitors

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Osmotic Diuretics

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Combination Diuretic Therapy

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Diuretics in Heart Failure

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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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