Diuretics Practice Questions

Q: At equally natriuretic doses, which of the following drugs causes maximum potassium excretion?

Acetazolamide. **Explanation:** The correct answer is **Acetazolamide**. **1. Why Acetazolamide is correct:** Acetazolamide is a Carbonic Anhydrase Inhibitor (CAI) that acts on the proximal convoluted tubule (PCT). It inhibits the reabsorption of sodium bicarbonate ($NaHCO_3$). This results in a large delivery of sodium and non-reabsorbable bicarbonate ions to the distal segments of the nephron. To compensate for the high sodium load, the distal tubule and collecting ducts exchange sodium for potassium. Furthermore, the presence of bicarbonate (a negative anion) in the distal tubule creates a negative luminal potential that further "pulls" $K^+$ out of the cells. Consequently, at doses that produce the same level of natriuresis as other diuretics, CAIs cause the **highest magnitude of potassium loss.** **2. Why the other options are incorrect:** * **Spironolactone:** This is a potassium-sparing diuretic. It antagonizes aldosterone receptors, leading to potassium retention rather than excretion. * **Furosemide:** While loop diuretics cause significant hypokalemia, their primary site of action is the Thick Ascending Limb. At *equally natriuretic doses*, the distal delivery of bicarbonate seen with CAIs makes Acetazolamide more potent at inducing kaliuresis. * **Aldosterone:** This is a mineralocorticoid, not a diuretic. While it increases $K^+$ excretion, it causes sodium *retention* (edema), making it the opposite of a natriuretic agent. **3. NEET-PG High-Yield Pearls:** * **Site of Action:** Acetazolamide (PCT), Furosemide (TAL of Loop of Henle), Thiazides (DCT). * **Metabolic Effect:** Acetazolamide causes **Hyperchloremic Metabolic Acidosis** (due to $HCO_3$ loss), whereas Loop and Thiazide diuretics cause **Metabolic Alkalosis**. * **Clinical Use:** Acetazolamide is the drug of choice for Glaucoma and Mountain Sickness, but it is a weak diuretic due to compensatory reabsorption in distal segments.

Q: Side effects of thiazides may include:

All of the above. Thiazide diuretics (e.g., Hydrochlorothiazide, Chlorthalidone) act on the **Distal Convoluted Tubule (DCT)** by inhibiting the $Na^+/Cl^-$ symporter [1]. Their side effect profile is a high-yield topic for NEET-PG, often remembered by the mnemonic **"Hyper-GLUC"** (Hyper-Glycemia, Lipidemia, Uricemia, Calcemia). ### **Explanation of Options:** * **Hypokalemia (Option A):** By inhibiting sodium reabsorption in the DCT, more sodium is delivered to the collecting ducts. This triggers the aldosterone-sensitive $Na^+/K^+$ exchange, leading to increased potassium excretion in the urine. * **Hyperuricemia (Option B):** Thiazides compete with uric acid for the organic acid secretory secretory transport system in the proximal tubule [1]. This decreases uric acid excretion, potentially precipitating **Gout** [1]. * **Hyperglycemia (Option C):** Thiazides cause hypokalemia, which inhibits the release of insulin from pancreatic beta cells (as insulin release is K-dependent). They also decrease peripheral glucose utilization, worsening glycemic control in diabetics. ### **Why "All of the Above" is Correct:** Since thiazides concurrently cause potassium loss, elevate serum uric acid levels, and impair glucose tolerance, all three listed side effects are characteristic of this drug class. ### **High-Yield Clinical Pearls for NEET-PG:** 1. **Hypercalcemia:** Unlike Loop diuretics (which cause hypocalcemia), Thiazides **increase** calcium reabsorption [1][2]. This makes them useful in treating **Idiopathic Hypercalciuria** (kidney stones). 2. **Hyponatremia:** Thiazides are a common cause of drug-induced hyponatremia, especially in elderly patients. 3. **Lipid Profile:** They can cause a transient increase in LDL cholesterol and triglycerides (**Hyperlipidemia**). 4. **Erectile Dysfunction:** A frequently overlooked but common clinical side effect of thiazides.

Q: Spironolactone is least commonly used in which of the following conditions?

Hypertension. The correct answer is **Hypertension**. While Spironolactone is a diuretic, it is considered a **weak diuretic** when used alone because it acts on the late distal tubule and collecting duct, where only about 2–3% of sodium reabsorption occurs [1]. In the management of essential hypertension, Thiazides or Calcium Channel Blockers are preferred as first-line agents. Spironolactone is typically reserved for resistant hypertension or specific cases where hyperaldosteronism is a contributing factor. **Why other options are incorrect:** * **Congestive Heart Failure (CHF):** Spironolactone is a cornerstone therapy (RALES trial). It prevents myocardial remodeling and fibrosis caused by aldosterone, significantly reducing mortality in patients with NYHA Class II-IV heart failure. * **Cirrhotic Edema:** It is the **drug of choice** for edema and ascites in liver cirrhosis. In cirrhosis, there is secondary hyperaldosteronism due to decreased hepatic clearance of aldosterone; Spironolactone directly antagonizes this effect [2]. * **Primary Hyperaldosteronism (Conn’s Syndrome):** It is used as the primary medical treatment to block the effects of excessive aldosterone secretion [1, 3], especially in patients who are not candidates for surgery. **NEET-PG High-Yield Pearls:** * **Mechanism:** Competitive antagonist at the Mineralocorticoid Receptor (MR) in the cortical collecting duct [1, 2, 3]. * **Side Effects:** Hyperkalemia (most common) [1, 3] and **Gynecomastia** (due to non-specific binding to androgen and progesterone receptors) [2]. * **Eplerenone:** A more selective mineralocorticoid antagonist with fewer endocrine side effects (no gynecomastia) [2]. * **Contraindication:** Should not be used if serum potassium is >5.0 mEq/L or in severe renal impairment (CrCl <30 mL/min) [1, 3].

Q: High ceiling diuretics are useful in the treatment of all of the following conditions except?

Pulmonary hypertension. **Explanation:** High-ceiling diuretics (Loop diuretics like Furosemide) act on the thick ascending limb of the Henle’s loop by inhibiting the **Na⁺-K⁺-2Cl⁻ symporter**. They are the most potent diuretics, capable of excreting up to 25% of filtered sodium. **Why Pulmonary Hypertension is the Correct Answer:** Pulmonary hypertension is primarily a vascular remodeling and vasoconstrictive disease. While diuretics may be used cautiously in associated right-sided heart failure to reduce congestion, they are **not** a primary treatment for pulmonary hypertension itself. The mainstay of treatment involves vasodilators (e.g., Sildenafil, Bosentan, Epoprostenol). In fact, aggressive diuresis can decrease preload too much, leading to a drop in cardiac output in these patients. **Analysis of Other Options:** * **Generalized Edema:** Loop diuretics are the first-line treatment for edema associated with Congestive Heart Failure (CHF), Nephrotic syndrome, and Liver cirrhosis due to their high efficacy. * **Cerebral Edema:** While Mannitol (Osmotic diuretic) is the drug of choice, high-dose loop diuretics are used as adjuncts to reduce intracranial pressure by decreasing CSF formation and inducing systemic dehydration. * **Acute Pulmonary Edema:** Furosemide is the **drug of choice**. It works via two mechanisms: a rapid **venodilatory effect** (mediated by prostaglandins) that reduces preload within minutes, followed by the slower diuretic effect. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** Furosemide is the DOC for Acute Pulmonary Edema and Hypercalcemia (with saline). * **Ototoxicity:** Ethacrynic acid is the most ototoxic; Furosemide is the most common cause of drug-induced deafness among diuretics. * **Metabolic Profile:** They cause "Hypo-everything" (Hypokalemia, Hyponatremia, Hypomagnesemia, Hypocalcemia) **except** Hyperuricemia and Hyperglycemia.

Q: Which of the following is the drug of choice for the treatment of inappropriate anti-diuretic hormone secretion?

Demeclocycline. ### Explanation **Correct Answer: D. Demeclocycline** **Mechanism and Rationale:** Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is characterized by excessive ADH release, leading to water retention and dilutional hyponatremia. **Demeclocycline**, a tetracycline derivative, is the drug of choice for chronic SIADH because it acts as an **ADH antagonist** at the level of the collecting duct. It induces a state of "nephrogenic diabetes insipidus" by interfering with the intracellular signaling (cAMP) triggered by ADH, thereby promoting the excretion of free water. **Analysis of Incorrect Options:** * **A. Furosemide:** While loop diuretics can be used in acute, symptomatic SIADH to increase free water clearance (usually alongside hypertonic saline), they are not the primary long-term treatment of choice. * **B. Hydrochlorothiazide:** Thiazides are contraindicated in SIADH. They inhibit sodium reabsorption in the distal tubule and can actually **worsen hyponatremia** by increasing ADH sensitivity and causing volume depletion-induced ADH release. * **C. Spironolactone:** This is a potassium-sparing diuretic (aldosterone antagonist) used primarily in hyperaldosteronism or heart failure; it has no role in antagonizing ADH. **High-Yield Clinical Pearls for NEET-PG:** * **Vaptans:** Tolvaptan (oral) and Conivaptan (IV) are "selective V2 receptor antagonists" and are now frequently preferred over demeclocycline for SIADH due to a better side-effect profile. * **Side Effect:** A major side effect of Demeclocycline is **nephrotoxicity** and photosensitivity. * **Correction Rate:** In SIADH, avoid rapid correction of hyponatremia to prevent **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis). Rule of thumb: <10–12 mEq/L in 24 hours. * **First-line treatment:** For mild/asymptomatic SIADH, the initial step is always **fluid restriction**.

Q: Hypercalcemia is seen in all of the following conditions except:

Loop diuretics. **Explanation:** The correct answer is **Loop diuretics** because they are the only option listed that causes **hypocalcemia** (decreased calcium levels) rather than hypercalcemia. **1. Why Loop Diuretics (Option C) is correct:** Loop diuretics (e.g., Furosemide) inhibit the **Na+/K+/2Cl- symporter** in the Thick Ascending Limb (TAL) of the Loop of Henle. This inhibition abolishes the positive transepithelial potential (lumen-positive voltage) that normally drives the paracellular reabsorption of divalent cations like **Calcium (Ca2+)** and **Magnesium (Mg2+)**. Consequently, calcium is excreted in the urine (hypercalciuria), leading to a decrease in serum calcium levels. **2. Why the other options are incorrect:** * **Lithium (Option A):** Lithium can cause hypercalcemia by increasing the set-point of the Calcium-Sensing Receptor (CaSR) in the parathyroid gland, leading to inappropriately high PTH secretion (Lithium-induced hyperparathyroidism). * **Multiple Myeloma (Option B):** This malignancy causes extensive bone resorption through the activation of osteoclasts by cytokines (RANKL, IL-6), leading to significant hypercalcemia. * **Hypervitaminosis D (Option D):** Vitamin D increases intestinal absorption of calcium and phosphate, as well as bone resorption, directly leading to elevated serum calcium levels. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** "Loop diuretics **Lose** calcium; Thiazides **Throw** it back into the blood." * **Thiazide Diuretics:** These cause **hypercalcemia** and are used in the management of idiopathic hypercalciuria to prevent calcium stones. * **Loop Diuretics:** These are used in the emergency management of **acute hypercalcemia** (along with aggressive saline hydration). * **Other causes of hypercalcemia:** Hyperparathyroidism (most common cause), Sarcoidosis (due to extra-renal 1-alpha hydroxylase activity), and Milk-Alkali Syndrome.

Q: Loop diuretics act by which of the following mechanisms?

Inhibition of Na+-K+-2 Cl- cotransport. **Explanation:** **Correct Option: B. Inhibition of Na+-K+-2 Cl- cotransport** Loop diuretics (e.g., Furosemide, Torsemide, Bumetanide) exert their primary effect by inhibiting the **Na+-K+-2Cl- (NKCC2) symporter** located in the luminal membrane of the **Thick Ascending Limb (TAL)** of the Loop of Henle. By blocking this transporter, these drugs prevent the reabsorption of sodium, potassium, and chloride. This leads to a significant increase in the excretion of these ions and water, making them the most potent diuretics ("High-ceiling" diuretics). **Analysis of Incorrect Options:** * **Option A (Na+-Cl- Symport):** This is the mechanism of action for **Thiazide diuretics**, which act on the Distal Convoluted Tubule (DCT). * **Option C (Na+-K+ ATPase):** This enzyme is located on the basolateral membrane of most renal cells. While it provides the energy gradient for transport, it is the primary target of **Cardiac Glycosides (Digoxin)**, not diuretics. * **Option D (H+-K+ ATPase):** This is the "proton pump" found in the gastric parietal cells. It is inhibited by **Proton Pump Inhibitors (PPIs)** like Omeprazole. **High-Yield Clinical Pearls for NEET-PG:** 1. **Site of Action:** Thick Ascending Limb (TAL) of the Loop of Henle. 2. **Electrolyte Changes:** Loop diuretics cause **Hypokalemia, Hypomagnesemia, and Hypocalcemia** (unlike Thiazides, which cause Hypercalcemia). 3. **Ototoxicity:** Ethacrynic acid is the most ototoxic, while Bumetanide is the least. 4. **Drug of Choice:** Furosemide is the drug of choice for **Acute Pulmonary Edema** due to its rapid action and additional venodilatory effect. 5. **Metabolic Effect:** They can cause **Hypokalemic Metabolic Alkalosis** and Hyperuricemia (precipitating Gout).

Q: On which part of the nephron do loop diuretics act?

Thick ascending limb. **Explanation:** **Mechanism of Action (The Correct Answer):** Loop diuretics (e.g., Furosemide, Torsemide, Bumetanide) primarily act on the **Thick Ascending Limb (TAL)** of the Loop of Henle [1, 2]. They work by inhibiting the **Na⁺-K⁺-2Cl⁻ symporter (NKCC2)** on the luminal membrane [1, 2]. By blocking this transporter, they prevent the reabsorption of sodium, potassium, and chloride, leading to potent natriuresis and diuresis [1]. Because the TAL is responsible for reabsorbing approximately 25% of filtered sodium, these are the most efficacious diuretics ("High-ceiling diuretics") [2]. **Analysis of Incorrect Options:** * **A. Descending limb:** This segment is highly permeable to water but impermeable to solutes. No major diuretics act here. * **C. Cortical segment:** This usually refers to the Distal Convoluted Tubule (DCT), which is the site of action for **Thiazide diuretics** (inhibiting the Na⁺-Cl⁻ symporter). * **D. Collecting duct:** This is the site of action for **Potassium-sparing diuretics** (e.g., Spironolactone, Amiloride) and ADH antagonists (Vaptans). **High-Yield Clinical Pearls for NEET-PG:** * **Abolition of Corticomedullary Gradient:** By inhibiting solute reabsorption in the TAL, loop diuretics interfere with the kidney's ability to concentrate urine. * **Calcium Excretion:** Unlike Thiazides (which cause hypercalcemia), loop diuretics cause **hypocalcemia** ("Loops lose Calcium"). They are used in the emergency management of hypercalcemia. * **Ototoxicity:** This is a unique side effect of loop diuretics (especially Ethacrynic acid) due to the presence of the NKCC transporter in the stria vascularis of the inner ear. * **Drug of Choice:** Furosemide is the drug of choice for acute pulmonary edema due to its rapid action and additional venodilatory effect.

Q: Mannitol when given intravenously causes which of the following changes?

Decrease in blood viscosity. **Explanation:** Mannitol is an osmotic diuretic that remains confined to the extracellular compartment. When administered intravenously, it creates an osmotic gradient that draws water from the intracellular space into the vascular compartment. **1. Why Option A is Correct:** The rapid shift of water from cells into the bloodstream leads to **hemodilution**. This expansion of plasma volume decreases the hematocrit and reduces the overall **blood viscosity**. This reduction in viscosity is clinically significant as it improves microcirculatory blood flow, particularly in the brain, which is one of the mechanisms by which mannitol reduces intracranial pressure (ICP). **2. Why the other options are incorrect:** * **Option B:** Mannitol decreases viscosity via hemodilution; it does not increase it. * **Option C:** While mannitol can increase renal blood flow, it does not consistently increase the **Glomerular Filtration Rate (GFR)**. In fact, its primary site of action is the Loop of Henle and the proximal tubule, where it limits water reabsorption. * **Option D:** Mannitol is used to **decrease** Intracranial Tension (ICT) and Intraocular Pressure (IOP) by drawing fluid out of the brain parenchyma and vitreous humor into the blood. It does not increase ICT. **High-Yield NEET-PG Pearls:** * **Mechanism:** Osmotic effect in the proximal tubule and descending limb of the Loop of Henle. * **Contraindications:** Acute Pulmonary Edema and Congestive Heart Failure (due to the initial rapid expansion of extracellular fluid volume) and Anuria. * **Clinical Uses:** Cerebral edema (to lower ICT), acute congestive glaucoma (to lower IOP), and prevention of cisplatin-induced nephrotoxicity. * **Side Effect:** Acute expansion of ECF can lead to "dialysis disequilibrium" or pulmonary congestion.

Question 1

At equally natriuretic doses, which of the following drugs causes maximum potassium excretion?

Accepted Answer

Acetazolamide

Answer

Spironolactone

Answer

Furosemide

Answer

Aldosterone

Question 2

Side effects of thiazides may include:

Accepted Answer

All of the above

Answer

Hypokalemia

Answer

Hyperuricemia

Answer

Hyperglycemia

Question 3

Spironolactone is least commonly used in which of the following conditions?

Accepted Answer

Hypertension

Answer

Congestive heart failure

Answer

Cirrhotic edema

Answer

Primary hyperaldosteronism

Question 4

High ceiling diuretics are useful in the treatment of all of the following conditions except?

Accepted Answer

Pulmonary hypertension

Answer

Generalized edema

Answer

Cerebral edema

Answer

Acute pulmonary edema

Question 5

Which of the following is the drug of choice for the treatment of inappropriate anti-diuretic hormone secretion?

Accepted Answer

Demeclocycline

Answer

Furosemide

Answer

Hydrochlorothiazide

Answer

Spironolactone

Question 6

Hypercalcemia is seen in all of the following conditions except:

Accepted Answer

Loop diuretics

Answer

Lithium

Answer

Multiple myeloma

Answer

Hypervitaminosis D

Question 7

Loop diuretics act by which of the following mechanisms?

Accepted Answer

Inhibition of Na+-K+-2 Cl- cotransport

Answer

Inhibition of Na+-Cl- Symport

Answer

Inhibition of Na+-K+ ATPase

Answer

Inhibition of H+-K+ ATPase

Question 8

A new diuretic is being studied in human volunteers. Compared with placebo, the new drug increases urine volume, decreases urinary Ca2+, increases body pH, and decreases serum K+. If this new drug has a similar mechanism of action to an established diuretic, it probably what?

Accepted Answer

Blocks the NaCl cotransporter in the distal convoluted tubule.

Answer

Blocks aldosterone receptors in the collecting tubule.

Answer

Inhibits carbonic anhydrase in the proximal convoluted tubule.

Answer

Inhibits the Na/K/2Cl cotransporter in the thick ascending limb.

Question 9

On which part of the nephron do loop diuretics act?

Accepted Answer

Thick ascending limb

Answer

Descending limb

Answer

Cortical segment

Answer

Collecting duct

Question 10

Mannitol when given intravenously causes which of the following changes?

Accepted Answer

Decrease in blood viscosity

Answer

Increase in blood viscosity

Answer

Increase in GFR

Answer

Increase in ICT

Diuretics — MCQs

Diuretics — MCQs

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