Diuretics — MCQs
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Which of the following potassium sparing diuretics cause renal stones?
Carbonic anhydrase inhibitors are:
Tolvaptan is used for:-
Mannitol is used in the management of:-
Assertion: Thiazide diuretics can cause hypercalcemia. Reason: Thiazides reduce urinary calcium excretion by acting on the distal convoluted tubule.
A 45-year-old man with chronic liver disease presents with ascites and severe edema. Which diuretic combination is most suitable to manage his condition?
Which diuretic acts on the loop of Henle?
What is the primary effect of acetazolamide when used at high altitudes?
A 70-year-old man with chronic heart failure is currently on optimal medical therapy with an ACE inhibitor, beta-blocker, and loop diuretic, but is experiencing worsening symptoms. Which diuretic should be added to his regimen to provide additional benefit?
Which type of diuretic is commonly prescribed for patients with heart failure to reduce fluid accumulation and manage blood pressure?
Diuretics Indian Medical PG Practice Questions and MCQs
Question 181: Which of the following potassium sparing diuretics cause renal stones?
- A. Triamterene (Correct Answer)
- B. Amiloride
- C. Eplerenone
- D. Spironolactone
Explanation: ***Triamterene*** - **Triamterene** is known particularly for its propensity to form **renal stones**, especially when combined with indomethacin or in patients with underlying kidney disease. - The drug itself is poorly soluble and can precipitate in the urine, forming stones or crystal aggregates. *Amiloride* - **Amiloride** is a potassium-sparing diuretic that inhibits sodium channels in the distal nephron, but it is **not associated with renal stone formation**. - Its mechanism of action does not involve precipitation in the urinary tract. *Eplerenone* - **Eplerenone** is a selective aldosterone receptor antagonist that prevents potassium excretion, but it has **not been linked to renal stone development**. - It works by blocking aldosterone's effects on the mineralocorticoid receptor, without crystal formation issues. *Spironolactone* - **Spironolactone** is a non-selective aldosterone antagonist, similar to eplerenone, and is **not recognized as a cause of renal stones**. - It competes with aldosterone for receptor binding in the collecting duct, leading to potassium sparing and sodium excretion.
Question 182: Carbonic anhydrase inhibitors are:
- A. Competitive and reversible inhibitors (Correct Answer)
- B. Noncompetitive and reversible inhibitors
- C. Competitive and irreversible inhibitors
- D. Noncompetitive and irreversible inhibitors
Explanation: ***Competitive and reversible inhibitors*** - Carbonic anhydrase inhibitors like **acetazolamide** bind to the zinc ion at the **active site** of the enzyme, making them competitive inhibitors. - They compete with the natural substrate (CO₂ and H₂O) for binding to the enzyme. - Their binding is **reversible**, meaning the inhibitor-enzyme complex can dissociate, and their effects can be overcome by increasing substrate concentration. - This is the **correct mechanism** of action for drugs like acetazolamide, methazolamide, and dorzolamide. *Competitive and irreversible inhibitors* - While carbonic anhydrase inhibitors are **competitive**, they are NOT irreversible. - Irreversible inhibitors form **covalent bonds** or cause permanent enzyme modification, which is not the case here. *Noncompetitive and irreversible inhibitors* - Carbonic anhydrase inhibitors do NOT bind to allosteric sites (noncompetitive mechanism). - They directly bind to the **active site zinc ion**, making them competitive, not noncompetitive. - They are also reversible, not irreversible. *Noncompetitive and reversible inhibitors* - This is incorrect because these drugs are **competitive inhibitors** that bind to the active site. - Noncompetitive inhibitors would bind at a site other than the active site, which does not describe carbonic anhydrase inhibitors.
Question 183: Tolvaptan is used for:-
- A. SIADH (Correct Answer)
- B. Von Willebrand disease
- C. Central DI
- D. Catecholamine resistant Shock
Explanation: ***SIADH*** - **Tolvaptan** is a **vasopressin V2 receptor antagonist** that promotes water excretion without affecting sodium, making it ideal for treating **euvolemic and hypervolemic hyponatremia** associated with SIADH. - In **syndrome of inappropriate antidiuretic hormone secretion (SIADH)**, there is excessive **ADH** leading to water retention and dilutional hyponatremia; tolvaptan effectively counters this by blocking vasopressin's action. *Von Willebrand disease* - This is a **bleeding disorder** caused by a deficiency or dysfunction of **von Willebrand factor**, treated with **desmopressin** or factor replacement, not tolvaptan. - Tolvaptan has no role in coagulation pathways or the management of bleeding disorders. *Central DI* - **Central diabetes insipidus (DI)** results from reduced **ADH production** by the hypothalamus or posterior pituitary, leading to excessive water loss. - It is treated with **desmopressin** (synthetic ADH) to replace the deficient hormone, which is the opposite effect of tolvaptan. *Catecholamine resistant Shock* - **Catecholamine-resistant shock** is characterized by persistent hypotension despite high doses of **vasopressors**. - Treatment often involves agents like **vasopressin** (not tolvaptan) or corticosteroids to improve vascular tone, as tolvaptan would worsen the hypotension by promoting diuresis.
Question 184: Mannitol is used in the management of:-
- A. Acute renal failure
- B. Pulmonary edema
- C. Congestive cardiac failure
- D. Acute angle-closure glaucoma (Correct Answer)
Explanation: ***Acute angle-closure glaucoma*** - **Mannitol** is an osmotic diuretic [1] used to rapidly reduce **intraocular pressure** in conditions like acute angle-closure glaucoma [2]. - It works by creating an **osmotic gradient** that draws fluid from the vitreous humor into the bloodstream [2]. - This is a well-established **emergency indication** for mannitol [2]. *Acute renal failure* - While mannitol may be used in **prevention** of acute kidney injury (e.g., in rhabdomyolysis, cardiovascular surgery) [2], its use in established acute renal failure is generally **contraindicated** if the patient is **anuric**, as it can exacerbate fluid overload [2]. - It is **not a primary management** for acute renal failure among the given options. *Pulmonary edema* - **Mannitol** is generally **contraindicated** in pulmonary edema because its initial effect is to increase **intravascular volume** [2], which can worsen fluid accumulation in the lungs. - Loop diuretics like **furosemide** are preferred for their rapid onset and profound diuretic effect in pulmonary edema. *Congestive cardiac failure* - **Mannitol** is typically **contraindicated** in congestive cardiac failure as it can cause a **transient increase in plasma volume**, potentially worsening cardiac workload and leading to decompensation [2]. - Diuretics commonly used in heart failure, such as **loop diuretics** (e.g., furosemide) or **thiazide diuretics**, are preferred to reduce fluid overload.
Question 185: Assertion: Thiazide diuretics can cause hypercalcemia. Reason: Thiazides reduce urinary calcium excretion by acting on the distal convoluted tubule.
- A. Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion
- B. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion (Correct Answer)
- C. Assertion is true, but Reason is false
- D. Assertion is false, but Reason is true
Explanation: ***Both Assertion and Reason are true, and Reason is the correct explanation of Assertion*** - Thiazide diuretics cause **hypercalcemia** by enhancing calcium reabsorption in the distal convoluted tubule (DCT) - By increasing Ca²⁺ reabsorption, thiazides **reduce urinary calcium excretion**, leading to elevated serum calcium levels - The mechanism described in the Reason directly explains why the Assertion occurs - Clinical relevance: This effect is beneficial in preventing **calcium-containing kidney stones** but can be problematic in patients with **hypercalcemia** or **hyperparathyroidism** *Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion* - Incorrect because the Reason (reduced urinary Ca²⁺ excretion at DCT) **is the direct mechanism** causing hypercalcemia - The two statements are causally linked, making this option wrong *Assertion is true, but Reason is false* - Incorrect because both statements are factually correct - Thiazides do reduce urinary calcium excretion via DCT action *Assertion is false, but Reason is true* - Incorrect because the Assertion is true - Thiazides are well-known to cause hypercalcemia, especially with chronic use
Question 186: A 45-year-old man with chronic liver disease presents with ascites and severe edema. Which diuretic combination is most suitable to manage his condition?
- A. Acetazolamide and Mannitol
- B. Spironolactone and Furosemide (Correct Answer)
- C. Metolazone and Torsemide
- D. Hydrochlorothiazide and Amiloride
Explanation: ***Spironolactone and Furosemide*** - **Spironolactone**, an **aldosterone antagonist**, is crucial because **secondary hyperaldosteronism** often contributes to sodium and water retention in patients with chronic liver disease and ascites. - **Furosemide**, a **loop diuretic**, provides potent diuresis by inhibiting sodium reabsorption in the **thick ascending limb of the loop of Henle**, effectively reducing fluid overload. *Acetazolamide and Mannitol* - **Acetazolamide**, a **carbonic anhydrase inhibitor**, has a relatively weak diuretic effect and is not typically used for significant ascites due to chronic liver disease. - **Mannitol**, an **osmotic diuretic**, is primarily used for cerebral edema or acute renal failure, not for chronic fluid retention in liver disease, as it can worsen volume status. *Metolazone and Torsemide* - **Metolazone**, a **thiazide-like diuretic**, can be effective in combination with loop diuretics for refractory edema but is not the first-line combination for initial management of ascites in chronic liver disease. - **Torsemide** is a loop diuretic, similar to furosemide, but typically not combined with metolazone as a primary strategy without prior trials of spironolactone and a loop diuretic. *Hydrochlorothiazide and Amiloride* - **Hydrochlorothiazide**, a **thiazide diuretic**, is less potent than loop diuretics and generally less effective in patients with advanced liver disease and significant ascites. - **Amiloride**, a **potassium-sparing diuretic**, is weaker than spironolactone and does not block aldosterone, making it less effective in combating the pathophysiology of ascites in liver disease.
Question 187: Which diuretic acts on the loop of Henle?
- A. Amiloride
- B. Thiazides
- C. Spironolactone
- D. Furosemide (Correct Answer)
Explanation: ***Furosemide*** - Furosemide is a **loop diuretic** that primarily acts on the **thick ascending limb of the loop of Henle**. - It inhibits the **Na+-K+-2Cl− cotransporter** (NKCC2), leading to increased excretion of sodium, potassium, and chloride. *Amiloride* - Amiloride is a **potassium-sparing diuretic** that acts on the **collecting duct**. - It inhibits the **epithelial sodium channel (ENaC)**, decreasing sodium reabsorption and potassium secretion. *Thiazides* - Thiazide diuretics (e.g., hydrochlorothiazide) act on the **distal convoluted tubule**. - They inhibit the **Na+-Cl− cotransporter**, reducing sodium reabsorption in this segment. *Spironolactone* - Spironolactone is an **aldosterone antagonist** that acts on the **collecting duct**. - It competitively inhibits aldosterone receptors, leading to decreased sodium reabsorption and increased potassium retention.
Question 188: What is the primary effect of acetazolamide when used at high altitudes?
- A. Elevate pH
- B. Decrease ventilation
- C. Reduce HCO3- (Correct Answer)
- D. Increase CO2
Explanation: ***Reduce HCO3-*** - Acetazolamide is a **carbonic anhydrase inhibitor**, which primarily acts on the kidneys to block **bicarbonate reabsorption**. - By reducing **bicarbonate levels (HCO3-)**, it induces a **metabolic acidosis**, which in turn stimulates **respiratory drive** and increases ventilation, thereby counteracting the effects of altitude sickness. *Elevate pH* - Acetazolamide causes a **metabolic acidosis**, leading to a *decrease* in blood pH, not an elevation. - The reduced pH is the stimulus for **increased ventilation**, which helps to normalize blood gases at altitude. *Decrease ventilation* - The **metabolic acidosis** induced by acetazolamide actually *stimulates* peripheral chemoreceptors, leading to an *increase* in ventilation. - Increased ventilation helps to **excrete CO2**, thereby improving oxygenation at high altitudes. *Increase CO2* - Increased ventilation (due to the **metabolic acidosis** induced by acetazolamide) leads to a *decrease* in partial pressure of **carbon dioxide (PCO2)**, not an increase. - This reduction in **PCO2** helps to improve the body's acid-base balance and oxygenation.
Question 189: A 70-year-old man with chronic heart failure is currently on optimal medical therapy with an ACE inhibitor, beta-blocker, and loop diuretic, but is experiencing worsening symptoms. Which diuretic should be added to his regimen to provide additional benefit?
- A. Furosemide
- B. Hydrochlorothiazide
- C. Mannitol
- D. Spironolactone (Correct Answer)
Explanation: ***Spironolactone*** - As an **aldosterone antagonist**, spironolactone is particularly indicated for **HFrEF (Heart Failure with reduced Ejection Fraction)** based on landmark trials like **RALES** and **EMPHASIS-HF**, providing additional diuretic effects and mortality benefit. - It's typically used as **add-on therapy** in patients already on **ACE inhibitors/ARBs** and **beta-blockers**, offering **cardioprotective benefits** by reducing myocardial fibrosis and improving ventricular remodeling. *Furosemide* - Furosemide is a **loop diuretic** often used as **first-line therapy** in heart failure for rapid symptom relief, but the question implies a patient already on a regimen needing *additional* relief. - While it can be **titrated upward**, adding another class of diuretic like an aldosterone antagonist provides **synergistic effects** and addresses different pathophysiological mechanisms. *Hydrochlorothiazide* - Hydrochlorothiazide is a **thiazide diuretic** typically used for **hypertension** or mild edema, which has **limited efficacy** in advanced heart failure due to reduced renal perfusion. - Its diuretic effect is generally **weaker than loop diuretics** and not usually the preferred add-on for worsening symptoms in chronic heart failure. *Mannitol* - Mannitol is an **osmotic diuretic** primarily used to reduce **intracranial** or **intraocular pressure**, not for chronic heart failure management. - It can **acutely increase intravascular volume**, which might worsen heart failure symptoms in patients with compromised cardiac function.
Question 190: Which type of diuretic is commonly prescribed for patients with heart failure to reduce fluid accumulation and manage blood pressure?
- A. Thiazide
- B. Loop (Correct Answer)
- C. Osmotic
- D. Carbonic anhydrase inhibitor
Explanation: ***Loop (Correct)*** - **Loop diuretics** are highly effective in removing significant amounts of fluid, making them ideal for managing **fluid overload** and **pulmonary congestion** in heart failure patients. - They work in the **loop of Henle** to inhibit Na+/K+/2Cl- co-transporters, leading to increased excretion of water, sodium, potassium, and chloride. - **First-line therapy** for acute decompensated heart failure and chronic heart failure with volume overload. *Thiazide (Incorrect)* - **Thiazide diuretics** are generally less potent than loop diuretics in inducing diuresis and are typically used for **mild to moderate hypertension** or edema. - Their primary site of action is the **distal convoluted tubule**, where they inhibit the Na+/Cl- co-transporter. - Not preferred in severe heart failure due to reduced efficacy in patients with decreased renal function. *Osmotic (Incorrect)* - **Osmotic diuretics**, such as mannitol, are primarily used to reduce **intracranial pressure** or **intraocular pressure** and are not routinely used for chronic fluid management in heart failure. - They exert their effect by creating an osmotic gradient in the renal tubules, drawing water into the lumen. *Carbonic anhydrase inhibitor (Incorrect)* - **Carbonic anhydrase inhibitors**, like acetazolamide, are mainly used for conditions such as **glaucoma**, **altitude sickness**, and to treat **metabolic alkalosis**. - They act in the **proximal convoluted tubule** to inhibit carbonic anhydrase, reducing bicarbonate reabsorption and leading to a mild diuretic effect. - Not used for heart failure management due to weak diuretic effect.
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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