Diuretics Practice Questions

Q: Mechanism of action of thiazides is by -

Inhibiting Na+/Cl- symporter in DCT. **Inhibiting Na+/Cl- symporter in DCT** - Thiazide diuretics primarily act on the **distal convoluted tubule (DCT)** of the nephron [2]. - They inhibit the **Na+/Cl- symporter** (NCC channel) on the apical membrane, preventing reabsorption of sodium and chloride ions [1], [2]. *Inhibiting Na+K+2CI- in descending limb of loop of henle* - The descending limb of the loop of Henle is permeable to water but largely impermeable to solutes; there is no significant Na+K+2Cl- symporter activity here. - This mechanism describes the action of loop diuretics, but they act on the **ascending** limb, not the descending limb. *Inhibiting Na+K+2Cl- in ascending limb of loop of henle* - This mechanism describes the action of **loop diuretics** (e.g., furosemide, bumetanide) [3]. - Loop diuretics inhibit the **Na+K+2Cl- cotransporter (NKCC2)** in the thick ascending limb of the loop of Henle, leading to significant diuresis [3]. *Inhibiting Na+/Cl- symporter in PCT* - The **proximal convoluted tubule (PCT)** is primarily responsible for reabsorbing most of the filtered sodium, chloride, bicarbonate, and other solutes. - While sodium is reabsorbed in the PCT, it's mainly through Na+/H+ exchangers and other mechanisms, not a specific Na+/Cl- symporter that is targeted by thiazides [2].

Q: Which of the following is NOT an effect of Mannitol?

Increases blood viscosity. ***Increases blood viscosity*** - Mannitol is an **osmotic diuretic** that works by increasing the osmolality of the blood plasma, which draws water from the interstitial fluid and intracellular compartments into the intravascular space. - This process leads to **hemodilution**, which would decrease blood viscosity rather than increase it. *Increases blood osmolality* - Mannitol, as an **osmotic diuretic**, directly works by increasing the osmolality of the plasma. - This elevated plasma osmolality creates an osmotic gradient that pulls water from cells and interstitial spaces into the blood. *Increases GFR* - By increasing plasma volume through the movement of fluid from the interstitial space, mannitol can lead to **increased renal blood flow** and, consequently, an elevated GFR. - The increased fluid volume delivered to the kidneys also contributes to its diuretic effect. *Decreases ICP* - Mannitol is frequently used to reduce **intracranial pressure** (ICP) because it draws water out of the brain parenchyma into the blood vessels due to its osmotic effect. - This reduction in brain volume lessens the pressure within the skull.

Q: All of the following diuretics increase K+ excretion EXCEPT:

Triamterene. ***Triamterene*** - **Triamterene** is a **potassium-sparing diuretic** that blocks epithelial sodium channels (ENaC) in the collecting duct, thereby reducing sodium reabsorption and potassium secretion. - Unlike most other diuretics, it causes **decreased K+ excretion** and can lead to hyperkalemia. *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** that acts in the proximal tubule, inhibiting bicarbonate reabsorption. - This leads to increased delivery of sodium and bicarbonate to the collecting duct, which enhances **potassium secretion** and increases K+ excretion. *Thiazide* - **Thiazide diuretics** (e.g., hydrochlorothiazide) act by inhibiting the Na+/Cl- cotransporter in the **distal convoluted tubule**. - This increases the delivery of sodium to the collecting duct, which stimulates the exchange of sodium for **potassium**, leading to increased K+ excretion and hypokalemia. *Furosemide* - **Furosemide** is a **loop diuretic** that inhibits the Na+/K+/2Cl- cotransporter in the **thick ascending limb of the loop of Henle**. - This prevents the reabsorption of these ions, leading to increased delivery of sodium to the collecting duct, which promotes **potassium secretion** and increased K+ excretion.

Q: All of the following are potassium sparing diuretic EXCEPT:

Indapamide. ***Indapamide*** - **Indapamide** is a **thiazide-like diuretic**, acting primarily on the distal convoluted tubule to inhibit sodium and chloride reabsorption, thus promoting their excretion along with water. - Unlike potassium-sparing diuretics, it can cause **potassium wasting (hypokalemia)** due to increased delivery of sodium to the collecting duct, where it is exchanged for potassium. *Triamterene* - **Triamterene** is a **potassium-sparing diuretic** that directly inhibits epithelial sodium channels (ENaC) in the collecting tubule, reducing sodium reabsorption and potassium secretion. - This mechanism helps to conserve potassium, preventing hypokalemia often associated with other diuretic classes. *Amiloride* - **Amiloride** is another **potassium-sparing diuretic** that, like triamterene, blocks epithelial sodium channels (ENaC) in the late distal tubule and collecting duct. - By inhibiting sodium reabsorption in this segment, it reduces the electrochemical gradient for potassium secretion, leading to potassium retention. *Spironolactone* - **Spironolactone** is an **aldosterone antagonist**, making it a potassium-sparing diuretic that competitively blocks aldosterone receptors in the collecting duct. - This blockage prevents aldosterone from promoting sodium reabsorption and potassium secretion, resulting in increased sodium excretion and **potassium retention**.

Q: Which of the following thiazides can be used in severe renal failure?

Metolazone. **Metolazone** - **Metolazone** is an exception among thiazides, as it retains its efficacy even in cases of **severe renal impairment** (creatinine clearance below 30 mL/min). - Its ability to act at more distal sites in the nephron and its different pharmacokinetic profile contribute to its effectiveness in reduced renal function. *Chlorthiazide* - This is a **thiazide diuretic** that loses significant efficacy when the **glomerular filtration rate (GFR)** falls below 30 mL/min. - It is generally not recommended for use in patients with **severe renal failure** due to diminished diuretic response. *Bendroflumethiazide* - Similar to most other **thiazide diuretics**, **bendroflumethiazide's** effectiveness is greatly reduced in **renal insufficiency**. - Its use is limited when the **creatinine clearance** drops below 30 mL/min, rendering it ineffective for diuresis in severe renal failure. *Trichloromethazide* - **Trichloromethazide** is another **thiazide diuretic** that shares the common characteristic of losing its diuretic effect in the presence of **significant renal impairment**. - It is not a suitable choice for managing fluid retention in patients with **severe renal failure**.

Q: Potassium-sparing diuretics act at the level of

Aldosterone receptor. ***Aldosterone receptor*** - **Potassium-sparing diuretics** include two main classes: 1. **Aldosterone receptor antagonists** (e.g., **spironolactone**, **eplerenone**) that act on **aldosterone receptors** in the collecting tubules 2. **ENaC blockers** (e.g., **amiloride**, **triamterene**) that directly block **epithelial sodium channels (ENaC)** in the collecting duct - Both mechanisms reduce **sodium reabsorption** and **potassium secretion** in the **collecting tubule**, leading to retained potassium. - The aldosterone receptor is the most commonly tested site for this drug class. *Carbonic anhydrase* - **Carbonic anhydrase inhibitors** (e.g., **acetazolamide**) act primarily in the **proximal convoluted tubule**. - They inhibit **bicarbonate reabsorption**, leading to diuresis and metabolic acidosis, and are not considered potassium-sparing. *NaCl symporter* - **Thiazide diuretics** act on the **NaCl symporter (NCC)** in the **distal convoluted tubule**. - They inhibit sodium and chloride reabsorption but do not spare potassium; chronic use can lead to **hypokalemia**. *Na-K pump* - The **Na-K pump** (Na+/K+-ATPase) is found in many cells and maintains ion gradients, but it is not the primary target of potassium-sparing diuretics. - While involved in renal transport, diuretics targeting this pump have different primary mechanisms and therapeutic uses.

Q: Which of the following statements accurately compares the potency of amiloride and triamterene?

Triamterene is more potent than amiloride. ***Triamterene is more potent than amiloride*** - **Triamterene** is generally considered to be **more potent** than amiloride, with approximately **10-fold greater potency** on a weight basis. - This higher potency is reflected in the **lower effective dosing** of triamterene (50-100 mg/day) compared to amiloride (5-10 mg/day), though the starting doses appear different due to available formulations. - Both are **potassium-sparing diuretics** that block epithelial sodium channels (ENaC) in the collecting duct, but triamterene requires a smaller dose to achieve equivalent diuretic effects. *Amiloride is more potent than triamterene* - This statement is incorrect; **amiloride** is typically considered **less potent** than triamterene on a milligram-per-milligram basis. - The standard therapeutic doses reflect this difference in potency, with amiloride requiring relatively higher doses for comparable effects. *Both drugs have equal potency* - This statement is incorrect as there are well-documented differences in the **potency** of these two **potassium-sparing diuretics**. - While both work through the same mechanism (blocking ENaC channels in the collecting tubule), their individual pharmacological profiles result in different dose-response relationships. *Potency cannot be compared between these drugs* - This statement is incorrect; the **potency** of drugs within the same class and mechanism of action, such as these two potassium-sparing diuretics, **can and should be compared**. - Clinical and pharmacological studies routinely assess and compare the relative potencies of similar therapeutic agents to guide appropriate dosing.

Q: Which one of the following diuretics causes increased concentration of Na+ & Cl- in urine with normal bicarbonate and is safe to use in patients with sulfonamide allergy?

Ethacrynic acid. ***Ethacrynic acid*** - Ethacrynic acid is a **loop diuretic** that inhibits the Na+-K+-2Cl- cotransporter in the **thick ascending limb of the loop of Henle**. - It causes increased urinary excretion of **Na+ and Cl-** while maintaining **normal bicarbonate levels** (does not affect carbonic anhydrase). - **Key distinguishing feature**: Ethacrynic acid is a **phenoxyacetic acid derivative** (NOT a sulfonamide), making it useful in patients with **sulfonamide allergies**. - Note: All loop diuretics share the property of increasing Na+ and Cl- excretion with normal bicarbonate. *Furosemide* - Furosemide is a **sulfonamide-derived loop diuretic** with the same mechanism as ethacrynic acid (inhibits Na+-K+-2Cl- cotransporter). - It also increases Na+ and Cl- excretion with normal bicarbonate levels. - While pharmacologically equivalent to ethacrynic acid for this effect, it is structurally different (sulfonamide derivative). *Bumetanide* - Bumetanide is another **sulfonamide-derived loop diuretic** with identical mechanism to furosemide and ethacrynic acid. - It produces the same electrolyte effects: increased Na+ and Cl- excretion with normal bicarbonate. - Structurally, it is a sulfonamide derivative like furosemide. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor** acting in the **proximal tubule**. - It increases excretion of **bicarbonate** (causing metabolic acidosis), along with Na+ and K+. - This would result in **elevated bicarbonate in urine**, NOT normal bicarbonate, making it incorrect.

Q: Which of the following diuretics can lead to erectile dysfunction?

Thiazide diuretics. ***Thiazide diuretics*** - **Thiazide diuretics** can cause **erectile dysfunction**, possibly due to effects on vascular function and **reduced blood flow** to the penis. - This adverse effect is a known concern and can impact patient adherence to **antihypertensive therapy**. *Carbonic anhydrase inhibitor* - **Carbonic anhydrase inhibitors** like acetazolamide are primarily used for glaucoma, altitude sickness, and metabolic alkalosis, and do not typically cause **erectile dysfunction**. - Their primary side effects relate to **metabolic acidosis** and electrolyte imbalances, not sexual function. *Loop diuretics* - **Loop diuretics** like furosemide are potent diuretics used in conditions like heart failure and edema; **erectile dysfunction** is not a common or significant side effect. - Their main adverse effects include **hypokalemia**, ototoxicity, and hypovolemia. *Mannitol* - **Mannitol** is an osmotic diuretic used to reduce intracranial and intraocular pressure. - It is administered intravenously and its side effects primarily involve **fluid and electrolyte disturbances**, not **erectile dysfunction**.

Q: Which of the following potassium sparing diuretics cause renal stones?

Triamterene. ***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 1

Mechanism of action of thiazides is by -

Accepted Answer

Inhibiting Na+/Cl- symporter in DCT

Answer

Inhibiting Na+K+2Cl- in ascending limb of loop of henle

Answer

Inhibiting Na+/Cl- symporter in PCT

Answer

Inhibiting Na+K+2Cl- in descending limb of loop of henle

Question 2

Which of the following is NOT an effect of Mannitol?

Accepted Answer

Increases blood viscosity

Answer

Increases blood osmolality

Answer

Increases GFR

Answer

Decreases ICP

Question 3

All of the following diuretics increase K+ excretion EXCEPT:

Accepted Answer

Triamterene

Answer

Acetazolamide

Answer

Thiazide

Answer

Furosemide

Question 4

All of the following are potassium sparing diuretic EXCEPT:

Accepted Answer

Indapamide

Answer

Triamterene

Answer

Amiloride

Answer

Spironolactone

Question 5

Which of the following thiazides can be used in severe renal failure?

Accepted Answer

Metolazone

Answer

Chlorthiazide

Answer

Bendroflumethiazide

Answer

Trichloromethazide

Question 6

Potassium-sparing diuretics act at the level of

Accepted Answer

Aldosterone receptor

Answer

Carbonic anhydrase

Answer

NaCl symporter

Answer

Na-K pump

Question 7

Which of the following statements accurately compares the potency of amiloride and triamterene?

Accepted Answer

Triamterene is more potent than amiloride

Answer

Amiloride is more potent than triamterene

Answer

Both drugs have equal potency

Answer

Potency cannot be compared between these drugs

Question 8

Which one of the following diuretics causes increased concentration of Na+ & Cl- in urine with normal bicarbonate and is safe to use in patients with sulfonamide allergy?

Accepted Answer

Ethacrynic acid

Answer

Furosemide

Answer

Bumetanide

Answer

Acetazolamide

Question 9

Which of the following diuretics can lead to erectile dysfunction?

Accepted Answer

Thiazide diuretics

Answer

Carbonic anhydrase inhibitor

Answer

Loop diuretics

Answer

Mannitol

Question 10

Which of the following potassium sparing diuretics cause renal stones?

Accepted Answer

Triamterene

Answer

Amiloride

Answer

Eplerenone

Answer

Spironolactone

Diuretics — MCQs

Diuretics — MCQs

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