Diuretics Practice Questions

Q: Carbonic anhydrase inhibitors are:

Competitive and reversible inhibitors. ***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.

Q: Mannitol is used in the management of:-

Acute angle-closure glaucoma. ***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.

Q: What is the mechanism of action of acetazolamide in the treatment of glaucoma?

Decreases aqueous production. ***Decreases aqueous production*** - **Acetazolamide** is a **carbonic anhydrase inhibitor** that acts on the **ciliary body** to reduce the formation of **bicarbonate ions** [2]. - This reduction in bicarbonate ions subsequently decreases the amount of fluid and solutes entering the **posterior chamber**, thereby lowering **aqueous humor production** and **intraocular pressure (IOP)** [2]. *Increases aqueous humor production* - This is incorrect; acetazolamide's therapeutic effect in glaucoma is specifically to **decrease** aqueous humor production [2]. - Increased aqueous humor production would lead to an **increase** in intraocular pressure, worsening glaucoma [1]. *Increases intraocular pressure* - This is incorrect; the primary goal of acetazolamide in glaucoma treatment is to **lower intraocular pressure**, not increase it [2]. - An increase in IOP is detrimental in glaucoma, leading to optic nerve damage [1]. *Decreases aqueous outflow* - This is incorrect; acetazolamide does not primarily affect the outflow pathways (e.g., **trabecular meshwork** or **uveoscleral outflow**) [1]. - A decrease in aqueous outflow would lead to an **increase in IOP**, which is contrary to the drug's intended action [1].

Q: Which diuretic acts on the loop of Henle?

Furosemide. ***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.

Q: What is the primary effect of acetazolamide when used at high altitudes?

Reduce HCO3-. ***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.

Q: Which type of diuretic is commonly prescribed for patients with heart failure to reduce fluid accumulation and manage blood pressure?

Loop. ***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.

Q: A 72-year-old male with chronic kidney disease has elevated serum potassium levels. Which drug is likely contributing to his hyperkalemia?

Spironolactone. **Spironolactone** - **Spironolactone** is a **potassium-sparing diuretic** [1, 2] that blocks aldosterone's effects [1], leading to **sodium excretion** and **potassium retention** [1]. - In patients with **chronic kidney disease (CKD)**, the kidneys' ability to excrete potassium is impaired, making them highly susceptible to **hyperkalemia** when taking spironolactone. *Furosemide* - **Furosemide** is a **loop diuretic** that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle. - This action leads to increased excretion of **sodium**, **potassium**, and chloride, making it more likely to cause **hypokalemia** rather than hyperkalemia. *Hydrochlorothiazide* - **Hydrochlorothiazide** is a **thiazide diuretic** that inhibits the Na-Cl cotransporter in the distal convoluted tubule. - It increases the excretion of **sodium** and **chloride**, and can lead to **potassium wasting**, typically causing **hypokalemia**. *Amlodipine* - **Amlodipine** is a **calcium channel blocker** used for hypertension and angina. - It primarily affects vascular smooth muscle and **does not directly influence potassium balance** or renal potassium handling.

Q: Gitelman's syndrome resembles the effects of which of the following drugs?

Thiazide diuretics. ***Thiazide diuretics*** - **Gitelman's syndrome** is a genetic disorder characterized by impaired function of the **thiazide-sensitive Na-Cl cotransporter (NCC)** in the distal convoluted tubule, functionally mimicking the effect of thiazide diuretics. - Both Gitelman's syndrome and thiazide diuretics cause **hypokalemia**, **hypomagnesemia**, **metabolic alkalosis**, and **hypocalciuria** due to impaired NCC function and secondary hyperaldosteronism. *Loop diuretics (Furosemide)* - Loop diuretics act on the **Na-K-2Cl cotransporter (NKCC2)** in the thick ascending limb of the loop of Henle, a more proximal site than the NCC. - While they also cause electrolyte abnormalities like hypokalemia, they typically lead to **hypercalciuria** rather than hypocalciuria, which is characteristic of Gitelman's syndrome. - Loop diuretic toxicity resembles **Bartter's syndrome**, not Gitelman's. *Potassium-sparing diuretics (Spironolactone)* - Spironolactone is an **aldosterone antagonist** that acts on the collecting duct, reducing sodium reabsorption and potassium secretion. - This drug primarily leads to **hyperkalemia**, which is the opposite of the hypokalemia seen in Gitelman's syndrome. *Carbonic anhydrase inhibitors (Acetazolamide)* - Acetazolamide inhibits carbonic anhydrase in the **proximal tubule**, reducing bicarbonate reabsorption. - This leads to **metabolic acidosis** with hypokalemia, which contrasts sharply with the **metabolic alkalosis** characteristic of Gitelman's syndrome.

Q: What is the most clinically significant electrolyte disturbance caused by loop diuretics?

Hypokalemia. ***Hypokalemia*** - Loop diuretics inhibit the **Na-K-2Cl cotransporter** in the **thick ascending limb** of the loop of Henle, increasing sodium delivery to the collecting duct. - This increased sodium delivery promotes potassium secretion by the principal cells in the collecting duct, leading to significant **potassium loss** in the urine and **hypokalemia**. - Hypokalemia is the **most clinically significant electrolyte disturbance** with loop diuretics, potentially causing cardiac arrhythmias, muscle weakness, and requiring routine monitoring and supplementation. - **Clinical relevance:** May necessitate potassium supplementation or concurrent use of potassium-sparing diuretics. *Dehydration* - While loop diuretics can cause volume depletion and dehydration due to increased diuresis, the question specifically asks about **electrolyte disturbances**. - Dehydration represents fluid volume loss rather than a specific electrolyte abnormality. *Hyperkalemia* - Loop diuretics cause **potassium loss**, not potassium retention. - Hyperkalemia would be expected with **potassium-sparing diuretics** (spironolactone, amiloride), not loop diuretics. - This is the **opposite** of the actual electrolyte effect. *Fluid retention* - Loop diuretics are prescribed specifically to **reduce fluid retention** (edema) by promoting diuresis. - Fluid retention is the therapeutic **indication** for loop diuretics, not a side effect. - This would represent therapeutic failure rather than an adverse effect.

Question 1

Carbonic anhydrase inhibitors are:

Accepted Answer

Competitive and reversible inhibitors

Answer

Noncompetitive and reversible inhibitors

Answer

Competitive and irreversible inhibitors

Answer

Noncompetitive and irreversible inhibitors

Question 2

Mannitol is used in the management of:-

Accepted Answer

Acute angle-closure glaucoma

Answer

Acute renal failure

Answer

Pulmonary edema

Answer

Congestive cardiac failure

Question 3

Assertion: Thiazide diuretics can cause hypercalcemia.
Reason: Thiazides reduce urinary calcium excretion by acting on the distal convoluted tubule.

Accepted Answer

Both Assertion and Reason are true, and Reason is the correct explanation of Assertion

Answer

Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion

Answer

Assertion is true, but Reason is false

Answer

Assertion is false, but Reason is true

Question 4

What is the mechanism of action of acetazolamide in the treatment of glaucoma?

Accepted Answer

Decreases aqueous production

Answer

Increases aqueous humor production

Answer

Increases intraocular pressure

Answer

Decreases aqueous outflow

Question 5

Which diuretic acts on the loop of Henle?

Accepted Answer

Furosemide

Answer

Amiloride

Answer

Thiazides

Answer

Spironolactone

Question 6

What is the primary effect of acetazolamide when used at high altitudes?

Accepted Answer

Reduce HCO3-

Answer

Elevate pH

Answer

Decrease ventilation

Answer

Increase CO2

Question 7

Which type of diuretic is commonly prescribed for patients with heart failure to reduce fluid accumulation and manage blood pressure?

Accepted Answer

Loop

Answer

Thiazide

Answer

Osmotic

Answer

Carbonic anhydrase inhibitor

Question 8

A 72-year-old male with chronic kidney disease has elevated serum potassium levels. Which drug is likely contributing to his hyperkalemia?

Accepted Answer

Spironolactone

Answer

Furosemide

Answer

Hydrochlorothiazide

Answer

Amlodipine

Question 9

Gitelman's syndrome resembles the effects of which of the following drugs?

Accepted Answer

Thiazide diuretics

Answer

Loop diuretics (Furosemide)

Answer

Potassium-sparing diuretics (Spironolactone)

Answer

Carbonic anhydrase inhibitors (Acetazolamide)

Question 10

What is the most clinically significant electrolyte disturbance caused by loop diuretics?

Accepted Answer

Hypokalemia

Answer

Dehydration

Answer

Hyperkalemia

Answer

Fluid retention

Diuretics — MCQs

Diuretics — MCQs

On this page

Practice by Chapter

Want unlimited practice?