Diuretics — MCQs
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Thiazides act on which part of the nephron?
Which diuretic exhibits paradoxical antidiuretic activity in diabetes insipidus?
Side effects of thiazide diuretics include all of the following except?
Which medication is commonly used in heart failure that also has aldosterone antagonistic properties?
Which of the following is an aldosterone antagonist?
How does amiloride differ from spironolactone in its mechanism of action?
The longest-acting loop diuretic is:
Which of the following is not associated with thiazide diuretics?
Which of the following statements about furosemide is TRUE?
Potassium secretion is decreased by action on the late distal tubule by which agent?
Diuretics Indian Medical PG Practice Questions and MCQs
Question 201: Thiazides act on which part of the nephron?
- A. Proximal Convoluted Tubule
- B. Descending limb of loop of Henle
- C. Glomerulus
- D. Distal Convoluted Tubule (Correct Answer)
Explanation: ***Distal Convoluted Tubule*** - **Thiazide diuretics** specifically inhibit the **sodium-chloride cotransporter (NCC)** in the apical membrane of cells in the distal convoluted tubule. - This inhibition leads to decreased reabsorption of sodium and chloride, resulting in increased excretion of water, sodium, and chloride. *Proximal Convoluted Tubule* - The proximal convoluted tubule is the primary site for reabsorption of the majority of filtered substances, including sodium, bicarbonate, glucose, and amino acids. - While some diuretics like **acetazolamide** (a carbonic anhydrase inhibitor) act here, thiazides do not. *Glomerulus* - The **glomerulus** is primarily responsible for the **filtration** of blood, forming the initial filtrate. - It is not a site for diuretic action as it does not participate in active reabsorption or secretion of electrolytes. *Descending limb of loop of Henle* - The descending limb is highly permeable to **water** but impermeable to solutes, leading to water reabsorption due to the hyperosmotic medulla. - Diuretics typically do not act on this segment to inhibit solute transport, though osmotic diuretics can affect water movement here.
Question 202: Which diuretic exhibits paradoxical antidiuretic activity in diabetes insipidus?
- A. Thiazide diuretics (Correct Answer)
- B. Aldosterone antagonists (Spironolactone)
- C. Loop diuretics (Furosemide)
- D. Potassium-sparing diuretics (Triamterene)
Explanation: ***Thiazide diuretics*** - Thiazides cause a modest **volume depletion**, leading to increased proximal tubular reabsorption of water and solutes [1]. - They also lower the **glomerular filtration rate**, further reducing the amount of fluid delivered to the collecting ducts, thus paradoxically reducing urine output in diabetes insipidus [2]. - This effect is particularly useful in **nephrogenic diabetes insipidus**, where the kidneys cannot respond to ADH [2]. *Potassium-sparing diuretics (Triamterene)* - Triamterene is a **potassium-sparing diuretic** that blocks epithelial sodium channels in the late distal tubule and collecting duct. - It increases sodium and water excretion, which would worsen, not improve, the polyuria of diabetes insipidus. *Aldosterone antagonists (Spironolactone)* - Spironolactone is a **mineralocorticoid receptor antagonist** that increases sodium and water excretion while conserving potassium in the collecting duct. - Its primary action is to counteract aldosterone, and it does not exhibit the paradoxical antidiuretic effect seen with thiazides in diabetes insipidus. *Loop diuretics (Furosemide)* - Loop diuretics like furosemide act on the **thick ascending limb of the loop of Henle** to inhibit sodium, potassium, and chloride reabsorption. - They cause significant diuresis and would **exacerbate the polyuria** in patients with diabetes insipidus, rather than improving it.
Question 203: Side effects of thiazide diuretics include all of the following except?
- A. Hypokalemia
- B. Erectile dysfunction
- C. Hyponatremia
- D. Hypocalcemia (Correct Answer)
Explanation: ***Hypocalcemia*** - Thiazide diuretics are known to cause **hypercalcemia** (increased calcium reabsorption), NOT hypocalcemia, due to their action on the distal convoluted tubule. - This property makes them useful in treating conditions like **idiopathic hypercalciuria** and **calcium-containing kidney stones**. - The mechanism involves enhanced passive calcium reabsorption in the proximal tubule and active reabsorption in the distal tubule. *Hyponatremia* - Thiazide diuretics impair the kidney's ability to dilute urine and reabsorb sodium in the distal tubule, leading to **increased sodium excretion** and potential hyponatremia. - This effect is more pronounced in **elderly patients** and those with increased free water intake. - Hyponatremia is one of the most common electrolyte disturbances with thiazides. *Hypokalemia* - Thiazides increase the delivery of sodium and water to the collecting duct, leading to increased activity of the **renin-angiotensin-aldosterone system** and enhanced potassium secretion. - This results in **potassium wasting** and hypokalemia, which may require potassium supplementation or combination with potassium-sparing diuretics. *Erectile dysfunction* - Thiazide diuretics can cause **erectile dysfunction** through mechanisms including effects on vascular smooth muscle, reduced blood flow, and possible hormonal effects. - This is a common side effect reported in male patients using these medications for hypertension and may affect compliance.
Question 204: Which medication is commonly used in heart failure that also has aldosterone antagonistic properties?
- A. Carvedilol
- B. Spironolactone (Correct Answer)
- C. Abiraterone
- D. Sacubitril/Valsartan
Explanation: ***Spironolactone*** - **Spironolactone** is a **potassium-sparing diuretic** that acts as a **competitive antagonist of aldosterone** receptors, primarily in the collecting ducts of the kidneys. - This action leads to increased excretion of sodium and water, and retention of potassium, which is beneficial in **heart failure** by reducing fluid overload and mitigating the detrimental effects of aldosterone on cardiac remodeling. *Carvedilol* - **Carvedilol** is a **beta-blocker** with additional **alpha-1 blocking** properties, commonly used in heart failure to reduce heart rate, blood pressure, and myocardial oxygen demand. - It does not possess significant aldosterone antagonistic properties. *Sacubitril/Valsartan* - **Sacubitril/Valsartan** is an **angiotensin receptor-neprilysin inhibitor (ARNI)**. Valsartan is an **angiotensin receptor blocker (ARB)**, and sacubitril inhibits neprilysin, an enzyme that degrades natriuretic peptides. - While it modulates the **renin-angiotensin-aldosterone system (RAAS)** and is highly effective in heart failure, it does not directly antagonize aldosterone receptors. *Abiraterone* - **Abiraterone** is an **androgen-biosynthesis inhibitor** used in the treatment of **prostate cancer**. - Its primary mechanism involves inhibiting **CYP17**, an enzyme critical for androgen production, and it has no role in the management of heart failure or aldosterone antagonism.
Question 205: Which of the following is an aldosterone antagonist?
- A. Furosemide
- B. Eplerenone (Correct Answer)
- C. Fenoldopam
- D. Deoxycorticosterone
Explanation: ***Eplerenone*** - **Eplerenone** acts as a **selective aldosterone antagonist**, blocking aldosterone receptors in epithelial tissues and various non-epithelial tissues. - Due to its selectivity, it causes fewer **endocrine side effects** (like gynecomastia or impotence) compared to spironolactone. *Fenoldopam* - **Fenoldopam** is a **dopamine D1-receptor agonist** that causes peripheral vasodilation and increased renal blood flow, primarily used for severe hypertension. - It does not directly interact with the **aldosterone pathway** and is not an aldosterone antagonist. *Furosemide* - **Furosemide** is a **loop diuretic** that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, leading to increased excretion of water, sodium, potassium, and chloride. - It does not directly block aldosterone's action but rather affects electrolyte reabsorption higher up in the nephron. *Deoxycorticosterone* - **Deoxycorticosterone (DOC)** is a **mineralocorticoid** hormone, a precursor to aldosterone, and functions as an agonist at the mineralocorticoid receptor. - It actually mimics the effects of aldosterone, promoting sodium and water retention, and is therefore not an aldosterone antagonist.
Question 206: How does amiloride differ from spironolactone in its mechanism of action?
- A. It is effective in conditions with normal or low aldosterone levels.
- B. It typically does not cause hypokalemia.
- C. It has a different mechanism of action that does not involve aldosterone receptor blockade.
- D. It acts primarily on the luminal side of the collecting duct cells. (Correct Answer)
Explanation: ***It acts primarily on the luminal side of the collecting duct cells.*** - **Amiloride** is a direct **epithelial sodium channel (ENaC) inhibitor** in the luminal membrane of the collecting duct, preventing sodium reabsorption and subsequent potassium excretion. - This mechanism is **aldosterone-independent**, distinguishing it from spironolactone, which antagonizes the aldosterone receptor. *It is effective in conditions with normal or low aldosterone levels.* - While amiloride is effective in these conditions, this statement does not directly describe its **mechanism of action** in differentiating it from spironolactone; both can be used. - The effectiveness of amiloride in normal or low aldosterone levels is a consequence of its **direct ENaC inhibition**, which is independent of aldosterone signaling. *It typically does not cause hypokalemia.* - This statement describes a **consequence** of amiloride's action (potassium-sparing effect) rather than its distinct mechanism compared to spironolactone. - Both amiloride and spironolactone are **potassium-sparing diuretics** and thus typically do not cause hypokalemia. *It has a different mechanism of action that does not involve aldosterone receptor blockade.* - This statement is true but is less precise about the specific **cellular location and target** of amiloride's action. - It broadly describes the difference but doesn't explain **how** amiloride directly intervenes in sodium transport at the cellular level.
Question 207: The longest-acting loop diuretic is:
- A. Torsemide (Correct Answer)
- B. Bumetanide
- C. Ethacrynic acid
- D. Furosemide
Explanation: ***Torsemide*** - **Torsemide** has a longer half-life (3.5 hours) compared to other loop diuretics, leading to a more sustained diuretic effect. - Its prolonged action contributes to its classification as the **longest-acting loop diuretic**, making it suitable for less frequent dosing. *Bumetanide* - **Bumetanide** has a rapid onset and short duration of action, with a half-life of about 1 to 1.5 hours. - While it is a potent loop diuretic, its duration of action is significantly shorter than that of torsemide. *Ethacrynic acid* - **Ethacrynic acid** has a duration of action of approximately 6-8 hours and a half-life of 2-4 hours. - Although it is unique as a non-sulfonamide loop diuretic, its duration of action is not the longest among this class. *Furosemide* - **Furosemide** typically has a half-life of about 1.5 to 2 hours, resulting in a relatively short duration of action (6-8 hours). - It is frequently administered multiple times a day due to its short-acting nature.
Question 208: Which of the following is not associated with thiazide diuretics?
- A. Hypercalciuria (Correct Answer)
- B. Hyponatremia
- C. Hypokalemia
- D. Hyperuricemia
Explanation: ***Hypercalciuria*** - Thiazide diuretics are known to **decrease urinary calcium excretion** (hypocalciuria), not increase it (hypercalciuria). - This effect makes them useful in preventing **recurrent calcium kidney stones**. *Hyponatremia* - Thiazides can cause **hyponatremia** by increasing the reabsorption of water (via ADH) and impairing salt reabsorption in the distal tubule, leading to reduced free water clearance. - This side effect is a common concern, especially in elderly patients. *Hypokalemia* - Thiazide diuretics inhibit sodium and chloride reabsorption in the distal convoluted tubule, leading to increased delivery of sodium to the collecting duct. - This increased sodium delivery, coupled with increased aldosterone secretion, promotes **potassium secretion** and can result in **hypokalemia**. *Hyperuricemia* - Thiazide diuretics compete with uric acid for secretion in the **proximal tubule**, leading to reduced uric acid excretion. - This can elevate **serum uric acid levels** and potentially precipitate gout attacks.
Question 209: Which of the following statements about furosemide is TRUE?
- A. It causes minimal diuresis.
- B. It can only be administered intravenously.
- C. It is used in the treatment of pulmonary edema. (Correct Answer)
- D. It primarily acts on the distal convoluted tubule.
Explanation: ***It is used in the treatment of pulmonary edema.*** - **Furosemide** is a potent **loop diuretic** that rapidly reduces **fluid overload**, making it highly effective in managing acute **pulmonary edema**. - Its ability to induce significant diuresis helps decrease systemic and pulmonary venous congestion, thereby improving respiratory function. *It can only be administered intravenously.* - While it can be administered **intravenously** for rapid effect, **furosemide** is also commonly available and effective when given **orally** [1]. - Oral administration is preferred for chronic management and outpatient settings. *It causes minimal diuresis.* - **Furosemide** is known as a **high-ceiling loop diuretic** because it produces a significant and rapid diuresis, not minimal [2]. - It works by inhibiting the **sodium-potassium-2 chloride cotransporter** [3] in the **thick ascending limb of the loop of Henle**, leading to substantial fluid and electrolyte excretion. *It primarily acts on the distal convoluted tubule.* - **Furosemide** primarily acts on the **thick ascending limb of the loop of Henle**, not the distal convoluted tubule [2]. - Diuretics that primarily act on the distal convoluted tubule are **thiazide diuretics**, such as hydrochlorothiazide [2].
Question 210: Potassium secretion is decreased by action on the late distal tubule by which agent?
- A. Spironolactone (Correct Answer)
- B. Thiazide
- C. Furosemide
- D. Acetazolamide
Explanation: ***Spironolactone*** - Spironolactone is a **potassium-sparing diuretic** that acts as an **aldosterone antagonist** in the **late distal tubule and collecting ducts**. - By blocking aldosterone receptors, it **decreases sodium reabsorption** and **inhibits potassium secretion**. - This is the only option that specifically acts on the late distal tubule to decrease potassium secretion. *Thiazide* - Thiazide diuretics act on the **early distal convoluted tubule (DCT)**, not the late distal tubule, to inhibit the Na+/Cl− cotransporter. - This typically leads to **increased potassium secretion** indirectly, as increased sodium delivery to the collecting duct drives potassium excretion. *Furosemide* - Furosemide is a **loop diuretic** that acts on the **thick ascending limb of the loop of Henle**, inhibiting the Na+/K+/2Cl− cotransporter. - Its action results in a significant increase in **potassium excretion** due to increased sodium delivery to the collecting duct. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor** that primarily acts on the **proximal convoluted tubule**. - It causes increased excretion of bicarbonate, sodium, and potassium, thus **increasing potassium secretion**, not decreasing it.
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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