Diuretics Practice Questions

Q: Acetazolamide is:

Competitive and reversible carbonic anhydrase inhibitor. ***Competitive and reversible carbonic anhydrase inhibitor*** - Acetazolamide is a **competitive inhibitor** that binds directly to the **zinc ion in the active site** of carbonic anhydrase. - It **competes with the natural substrate (CO2/HCO3-)** for binding to the active site, which is the hallmark of competitive inhibition. - It is a **reversible inhibitor**, meaning it eventually dissociates from the enzyme and its effects are not permanent. - As a sulfonamide derivative, it mimics the substrate and blocks the enzyme's catalytic activity temporarily. *Competitive and irreversible carbonic anhydrase inhibitor* - While acetazolamide is indeed a **competitive inhibitor**, it is **not irreversible**. - An irreversible inhibitor forms a **permanent covalent bond** with the enzyme, which acetazolamide does not do. - The drug's effects wear off as it is metabolized and excreted, demonstrating its reversible nature. *Non-competitive and reversible carbonic anhydrase inhibitor* - This option is incorrect because acetazolamide **does not bind to an allosteric site**. - It binds directly to the **active site zinc ion**, making it a competitive inhibitor, not non-competitive. - Non-competitive inhibitors bind to sites other than the active site and cannot be overcome by increasing substrate concentration. *Non-competitive and irreversible carbonic anhydrase inhibitor* - Acetazolamide is neither **non-competitive** nor **irreversible**. - It binds to the **active site** (competitive mechanism) and its binding is **reversible**. - This option combines two incorrect characteristics of the drug's mechanism of action.

Q: In the presence of renal failure, which of the following should not be given?

Spironolactone. ***Spironolactone*** - **Spironolactone** is an **aldosterone antagonist**, a **potassium-sparing diuretic**, which can cause **hyperkalemia**, especially in patients with **renal impairment** where potassium excretion is already compromised - Due to the risk of severe **hyperkalemia**, which can lead to life-threatening **cardiac arrhythmias**, spironolactone is **contraindicated** or used with extreme caution in **renal failure** - In renal failure, the kidneys cannot adequately excrete potassium, and adding a potassium-sparing diuretic significantly increases the risk of dangerous hyperkalemia *Bumetanide* - **Bumetanide** is a **loop diuretic** that primarily acts on the **ascending limb of the loop of Henle** to inhibit sodium and chloride reabsorption - While its efficacy may be reduced in severe renal failure, it is still commonly used at higher doses and can be effective in managing fluid overload in these patients - Loop diuretics remain the mainstay of diuretic therapy in renal failure, unlike potassium-sparing diuretics *Furosemide* - **Furosemide** is another **loop diuretic** that is often used in patients with **renal failure** to promote diuresis and manage fluid overload - Even with impaired kidney function, it can still exert its diuretic effect, although higher doses may be required - It does not cause significant potassium retention and is safe to use in renal failure *None of the options* - This option is incorrect because **spironolactone** is specifically contraindicated in patients with **renal failure** due to the high risk of **hyperkalemia**

Q: All of the following adverse effects can be caused by loop diuretics except :

Hypercalcemia. ***Hypercalcemia*** - Loop diuretics inhibit the reabsorption of calcium in the thick ascending limb of the loop of Henle, leading to **increased calcium excretion** and thus **hypocalcemia**, not hypercalcemia [2]. - This property makes them useful in treating conditions like hypercalcemia, but it means they do not cause hypercalcemia themselves. *Hypomagnesemia* - Loop diuretics inhibit magnesium reabsorption in the thick ascending limb, leading to **increased urinary magnesium excretion** and potential **hypomagnesemia** [1], [2]. - This electrolyte imbalance can contribute to cardiac arrhythmias and muscle weakness [2]. *Hyperglycemia* - Loop diuretics, particularly in high doses, can decrease **insulin secretion** and increase **insulin resistance**, leading to **hyperglycemia**. - This effect is generally mild but can be significant in patients with **diabetes mellitus**. *Hyperuricemia* - Loop diuretics compete with uric acid for secretion into the renal tubules, leading to **reduced uric acid excretion** and elevated serum uric acid levels, also known as **hyperuricemia** [1]. - This can precipitate or exacerbate **gout attacks** in susceptible individuals [1].

Q: Thiazide diuretics cause all except:

Increased calcium excretion. ***Increased calcium excretion*** - Thiazide diuretics are known to **decrease urinary calcium excretion**, leading to an increase in serum calcium levels. - This property makes them useful in the treatment of **calcium nephrolithiasis** and **osteoporosis**. *Decreased uric acid excretion* - Thiazide diuretics compete with uric acid for secretion in the **proximal tubule**, leading to decreased uric acid excretion and potential **hyperuricemia**. - This can precipitate or exacerbate **gout**. *Hyperkalemia* - Thiazide diuretics cause **hypokalemia**, NOT hyperkalemia, by increasing potassium excretion in the **distal convoluted tubule**. - Thiazides block Na-Cl cotransporter, leading to increased sodium delivery to collecting duct where **sodium-potassium exchange** occurs, causing potassium loss. *Hyperglycemia* - Thiazide diuretics can cause **hyperglycemia** by impairing insulin secretion from the pancreas and increasing insulin resistance in peripheral tissues. - This effect is more prominent in patients with **pre-existing diabetes** or impaired glucose tolerance.

Q: Which potassium-sparing diuretic alters cardiac morphology and is associated with anti-androgenic side effects?

Spironolactone. ***Spironolactone*** - **Spironolactone** is a **non-selective aldosterone antagonist** that blocks mineralocorticoid receptors - It has significant **anti-androgenic effects** due to binding to androgen receptors, causing gynecomastia, decreased libido, and menstrual irregularities - Aldosterone promotes **cardiac remodeling** (hypertrophy and fibrosis) in heart failure; spironolactone's antagonistic action **reverses or prevents** these detrimental changes, thus altering cardiac morphology favorably - Used in **heart failure with reduced ejection fraction** (HFrEF) to improve outcomes and reduce mortality *Amiloride* - **Amiloride** is a direct epithelial sodium channel (ENaC) blocker - Its primary action is to inhibit sodium reabsorption in the collecting tubule - While it helps in treating hypertension and heart failure through its diuretic effect, it does **not directly alter cardiac morphology** like aldosterone antagonists - No anti-androgenic effects *Triamterene* - **Triamterene** is another direct ENaC blocker, similar in mechanism to amiloride - Promotes sodium excretion and potassium retention, often combined with loop or thiazide diuretics - Does **not have direct effects on aldosterone-mediated cardiac remodeling** - No anti-androgenic effects *Eplerenone* - **Eplerenone** is a **selective aldosterone receptor antagonist**, similar to spironolactone in altering cardiac morphology - However, it is **more selective** for mineralocorticoid receptors and has **minimal anti-androgenic effects** - This selectivity reduces hormonal side effects like gynecomastia - Also used in heart failure and post-MI, but the question specifically asks about the drug associated with anti-androgenic effects

Q: Chronic thiazide therapy causes persistent hypercalcemia which is due to:

Increased distal tubular calcium reabsorption. ***Increased distal tubular calcium reabsorption*** - Thiazide diuretics work by inhibiting the **sodium-chloride cotransporter** in the **distal convoluted tubule**, leading to increased sodium and water excretion. - This inhibition also leads to enhanced **calcium reabsorption** in the distal tubule by increasing the electrochemical gradient and affecting transmembrane calcium channels, resulting in **hypercalcemia**. *Fanconi's syndrome* - This is a generalized dysfunction of the **proximal renal tubules**, leading to the excretion of amino acids, glucose, phosphate, and bicarbonate in the urine. - It typically causes **hypophosphatemia** and **renal osteodystrophy**, not primary hypercalcemia. *Hypervitaminosis D* - This condition results from excessive intake of **vitamin D**, leading to increased intestinal calcium absorption and bone resorption, causing hypercalcemia. - It is not directly caused by chronic thiazide therapy. *Renal tubular acidosis* - This is a group of disorders characterized by a defect in renal acid excretion or bicarbonate reabsorption, leading to **metabolic acidosis**. - While it can be associated with various electrolyte disturbances, it does not directly cause persistent hypercalcemia.

Q: Amiloride can cause hyperkalemia due to its action on:

Electrogenic Na+ channels. ***Correct: Electrogenic Na+ channels*** - Amiloride is a **potassium-sparing diuretic** that blocks the **epithelial sodium channels (ENaC)** in the apical membrane of the collecting duct cells. - By blocking **ENaC**, amiloride reduces the reabsorption of sodium, which in turn diminishes the negative potential in the tubular lumen, thereby reducing the driving force for **potassium secretion** and leading to hyperkalemia. *Incorrect: Electrogenic K+ channels* - While potassium channels are involved in potassium balance, amiloride's primary action is not directly on these channels. - Its effects on potassium are secondary to its impact on sodium reabsorption and the resulting electrochemical gradient. *Incorrect: Non-electrogenic Na+-Cl- symporter* - The **Na+-Cl- symporter (NCC)** is located in the distal convoluted tubule and is the target of **thiazide diuretics**, not amiloride. - Blocking NCC leads to increased delivery of sodium and water to the collecting duct, but does not directly cause hyperkalemia. *Incorrect: H+-K+ ATPase* - The **H+-K+ ATPase** in the collecting duct is involved in potassium reabsorption and hydrogen ion secretion. - Amiloride does not directly inhibit this pump; instead, it affects potassium handling by altering the electrical gradient associated with sodium reabsorption.

Q: Thiazides and loop diuretics both have opposite action on which of the following ions ?

Calcium. ***Calcium*** - Thiazide diuretics **increase calcium reabsorption** in the distal convoluted tubule, leading to decreased urinary calcium excretion. - Loop diuretics **decrease calcium reabsorption** in the thick ascending limb of the loop of Henle, resulting in increased urinary calcium excretion. *Potassium* - Both thiazide and loop diuretics can cause **hypokalemia** by increasing potassium excretion in the urine. - This is due to increased sodium delivery to the collecting duct, which stimulates potassium secretion. *Sodium* - Both thiazide and loop diuretics inhibit sodium reabsorption at different sites in the nephron, leading to **increased urinary sodium excretion** (natriuresis). - This is their primary mechanism of action for diuresis. *Chloride* - Both thiazide and loop diuretics inhibit **chloride reabsorption** as they block specific sodium-chloride cotransporters. - Thiazides inhibit the Na-Cl cotransporter in the DCT, while loop diuretics inhibit the Na-K-2Cl cotransporter in the thick ascending limb.

Q: Furosemide causes all except -

Hypercalcemia. ***Hypercalcemia*** - Furosemide, a **loop diuretic**, inhibits the reabsorption of calcium in the thick ascending limb of the loop of Henle, leading to increased urinary calcium excretion and thus **hypocalcemia**, not hypercalcemia. - This effect makes loop diuretics useful in managing **hypercalcemia** by promoting calcium excretion. *Hypokalemia* - Furosemide inhibits the Na-K-2Cl cotransporter, leading to increased delivery of sodium to the collecting duct, which enhances potassium secretion and can cause **hypokalemia**. - Monitoring serum potassium levels and potassium supplementation are often necessary during furosemide therapy. *Ototoxicity* - Furosemide can cause **ototoxicity**, particularly with rapid intravenous administration or in patients with renal impairment. - This adverse effect typically manifests as **tinnitus** or **hearing loss**, which can be transient or permanent. *Hyperuricemia* - Furosemide competes with uric acid for secretion in the proximal tubule, leading to decreased uric acid excretion and subsequently **hyperuricemia**. - This can precipitate or exacerbate **gout attacks** in susceptible individuals.

Q: A drug that can be used for producing alkalinization of urine is?

Acetazolamide. ***Acetazolamide*** - This drug is a **carbonic anhydrase inhibitor** that works in the **proximal tubule** of the kidney to decrease bicarbonate reabsorption. - By inhibiting **carbonic anhydrase**, it increases the excretion of **bicarbonate**, leading to an **alkaline urine** and mild systemic acidosis. *Spironolactone* - This is a **potassium-sparing diuretic** that acts as an **aldosterone antagonist** in the collecting duct. - It increases sodium excretion and potassium retention, but does not primarily cause **urine alkalinization**. *Furosemide* - This is a **loop diuretic** that acts on the **thick ascending limb of the loop of Henle** to inhibit the Na-K-2Cl cotransporter. - While it can increase urine output, it primarily increases the excretion of sodium, potassium, and chloride, and typically causes a **mild metabolic alkalosis** in the blood, but does not directly alkalinize the urine. *Hydrochlorothiazide* - This is a **thiazide diuretic** that acts in the **distal convoluted tubule** to inhibit the Na-Cl cotransporter. - It promotes the excretion of sodium and chloride, and can cause **hypokalemia** and metabolic alkalosis, but does not primarily induce **urine alkalinization**.

Question 1

Acetazolamide is:

Accepted Answer

Competitive and reversible carbonic anhydrase inhibitor

Answer

Non-competitive and irreversible carbonic anhydrase inhibitor

Answer

Non-competitive and reversible carbonic anhydrase inhibitor

Answer

Competitive and irreversible carbonic anhydrase inhibitor

Question 2

In the presence of renal failure, which of the following should not be given?

Accepted Answer

Spironolactone

Answer

Bumetanide

Answer

Furosemide

Answer

None of the options

Question 3

All of the following adverse effects can be caused by loop diuretics except :

Accepted Answer

Hypercalcemia

Answer

Hypomagnesemia

Answer

Hyperglycemia

Answer

Hyperuricemia

Question 4

Thiazide diuretics cause all except:

Accepted Answer

Increased calcium excretion

Answer

Decreased uric acid excretion

Answer

Hyperkalemia

Answer

Hyperglycemia

Question 5

Which potassium-sparing diuretic alters cardiac morphology and is associated with anti-androgenic side effects?

Accepted Answer

Spironolactone

Answer

Amiloride

Answer

Triamterene

Answer

Eplerenone

Question 6

Chronic thiazide therapy causes persistent hypercalcemia which is due to:

Accepted Answer

Increased distal tubular calcium reabsorption

Answer

Fanconi's syndrome

Answer

Hypervitaminosis D

Answer

Renal tubular acidosis

Question 7

Amiloride can cause hyperkalemia due to its action on:

Accepted Answer

Electrogenic Na+ channels

Answer

Electrogenic K+ channels

Answer

Non-electrogenic Na+-Cl- symporter

Answer

H+-K+ ATPase

Question 8

Thiazides and loop diuretics both have opposite action on which of the following ions ?

Accepted Answer

Calcium

Answer

Potassium

Answer

Sodium

Answer

Chloride

Question 9

Furosemide causes all except -

Accepted Answer

Hypercalcemia

Answer

Hypokalemia

Answer

Ototoxicity

Answer

Hyperuricemia

Question 10

A drug that can be used for producing alkalinization of urine is?

Accepted Answer

Acetazolamide

Answer

Spironolactone

Answer

Furosemide

Answer

Hydrochlorothiazide

Diuretics — MCQs

Diuretics — MCQs

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