Diuretics Practice Questions

Q: Which diuretic can be used in renal failure?

Furosemide. **Explanation:** **Furosemide** is the correct answer because it is a high-ceiling loop diuretic that remains effective even when the Glomerular Filtration Rate (GFR) falls below 30 mL/min. In renal failure, the delivery of solutes to the distal nephron is reduced; loop diuretics are potent enough to inhibit the $Na^+-K^+-2Cl^-$ symporter in the thick ascending limb, maintaining diuresis and managing fluid overload in patients with chronic kidney disease (CKD). **Why the other options are incorrect:** * **Chlorothiazide & Chlorthalidone:** These are Thiazide/Thiazide-like diuretics. They generally lose their efficacy when GFR is less than 30 mL/min (except for Metolazone and Indapamide). Using them in advanced renal failure is ineffective for fluid management. * **Mannitol:** This is an osmotic diuretic. In renal failure, Mannitol is not excreted efficiently, leading to its accumulation in the extracellular fluid. This causes "osmotic shift," drawing water out of cells and potentially leading to acute pulmonary edema or congestive heart failure. It is contraindicated in established anuria. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Furosemide is the drug of choice for acute pulmonary edema and edema associated with CKD. * **Metolazone Exception:** While most thiazides fail in renal failure, Metolazone can be combined with Loop diuretics (Sequential Nephron Blockade) to treat refractory edema in CKD patients. * **Ototoxicity:** Furosemide can cause dose-dependent ototoxicity, especially when administered rapidly IV or combined with aminoglycosides. * **Electrolyte Profile:** Loop diuretics cause "Hypo-everything" (Hypokalemia, Hypomagnesemia, Hypocalcemia), except for Hyperuricemia and Hyperglycemia.

Q: Which of the following side effects is associated with Spironolactone?

Hyperkalemia. **Explanation:** **Spironolactone** is a potassium-sparing diuretic that acts as a competitive antagonist of the **Mineralocorticoid Receptor (Aldosterone receptor)** in the late distal tubule and collecting duct. **Why Hyperkalemia is Correct:** Aldosterone normally promotes the reabsorption of sodium ($Na^+$) and the excretion of potassium ($K^+$) and hydrogen ions ($H^+$). By blocking this receptor, Spironolactone prevents $K^+$ secretion into the tubular lumen. This leads to the retention of potassium in the blood, resulting in **Hyperkalemia**, its most significant and potentially life-threatening side effect. **Analysis of Incorrect Options:** * **A. Alkalosis:** Spironolactone causes **Metabolic Acidosis** (not alkalosis) because it inhibits the excretion of $H^+$ ions. * **B. Hirsutism:** Spironolactone actually has **anti-androgenic** properties (it blocks androgen receptors and inhibits steroidogenesis). Therefore, it is used to *treat* hirsutism in conditions like PCOS. A common side effect in males, however, is **gynecomastia**. * **D. Hyperglycemia:** This is a classic side effect of **Thiazides and Loop diuretics**, which can impair insulin release. Spironolactone does not typically affect blood glucose levels. **High-Yield Clinical Pearls for NEET-PG:** * **Eplerenone** is a more selective aldosterone antagonist with fewer endocrine side effects (less risk of gynecomastia) compared to Spironolactone. * **Drug Interaction:** Avoid combining Spironolactone with ACE inhibitors or ARBs, as this significantly increases the risk of severe hyperkalemia. * **Indication of Choice:** It is the diuretic of choice for patients with **Cirrhosis with Ascites** and is proven to reduce mortality in **Chronic Heart Failure (NYHA Class II-IV)**.

Q: A 64-year-old man with heart failure is recently started on 80 mg/day of furosemide. He now feels weak and tired, but notes that his heart failure symptoms have improved. There is no change in his urine output and he gets a good diuretic response every time he takes his furosemide. Which are the characteristic ECG findings?

lengthened QU interval. ### Explanation **Correct Answer: C. Lengthened QU interval** **1. Underlying Medical Concept:** Furosemide is a potent loop diuretic that inhibits the Na⁺/K⁺/2Cl⁻ symporter in the thick ascending limb of the Loop of Henle. A common and significant side effect of loop diuretics is **hypokalemia** (low serum potassium). In hypokalemia, the ECG undergoes characteristic changes due to delayed ventricular repolarization. The most classic finding is the appearance of **prominent U waves**. As the U wave becomes more pronounced and the T wave flattens, the T and U waves often merge. This creates the appearance of a **"lengthened QU interval"** (or a pseudo-prolonged QT interval), which is a hallmark of potassium depletion. The patient’s symptoms of weakness and fatigue are clinical indicators of this electrolyte imbalance. **2. Why the other options are incorrect:** * **A & B (PR Interval):** Changes in the PR interval are typically associated with calcium abnormalities or AV nodal blocks (e.g., Digoxin toxicity), not primarily with the hypokalemia caused by diuretics. * **D (Shortened QT interval):** A shortened QT interval is characteristic of **hypercalcemia**. In contrast, hypokalemia (and hypocalcemia) typically leads to a prolonged appearance of the repolarization phase (prolonged QU/QT). **3. NEET-PG High-Yield Pearls:** * **ECG findings in Hypokalemia:** Flattening/inversion of T waves, ST-segment depression, prominent U waves, and QU prolongation. * **Loop Diuretics Side Effects (Mnemonic: OH DANG!):** **O**totoxicity, **H**ypokalemia, **D**ehydration, **A**llergy (sulfa), **N**ephritis (interstitial), **G**out (hyperuricemia). * **Metabolic state:** Loop diuretics cause **Hypokalemic Metabolic Alkalosis**. * **U wave:** A positive deflection after the T wave, representing slow repolarization of Purkinje fibers. It is most visible in precordial leads V2–V4.

Q: Which of the following drugs prevents renal stones?

Acetazolamide. The correct answer is **Acetazolamide**. This question focuses on the specific management of **Cystinuria** and the prevention of **Cystine stones**. **1. Why Acetazolamide is correct:** Acetazolamide is a Carbonic Anhydrase inhibitor that acts on the proximal convoluted tubule [1, 2]. By inhibiting the reabsorption of bicarbonate, it increases urinary bicarbonate excretion, leading to **alkalinization of the urine** [1, 2]. Cystine is highly insoluble in acidic urine but becomes significantly more soluble as the pH rises above 7.5. Therefore, by making the urine alkaline, Acetazolamide prevents the precipitation of cystine crystals and the formation of renal stones in patients with cystinuria [1]. **2. Why the other options are incorrect:** * **Hydrochlorothiazide:** While Thiazides are used to prevent **Calcium Oxalate** stones (by increasing distal tubular calcium reabsorption and reducing hypercalciuria) [3], they do not prevent cystine stones. * **Mannitol:** This is an osmotic diuretic used primarily to reduce intracranial or intraocular pressure. It has no specific role in stone prevention. * **Furosemide:** This loop diuretic **increases** urinary calcium excretion (hypercalciuria) [3]. Consequently, it can actually promote the formation of calcium-containing renal stones. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice for Hypercalciuria stones:** Thiazides (e.g., Chlorthalidone, Hydrochlorothiazide) [3]. * **Drug that causes stones:** Acetazolamide can paradoxically cause **Calcium Phosphate** stones because alkaline urine promotes calcium phosphate precipitation, even though it prevents cystine stones [1, 2]. * **Loop Diuretics (Furosemide):** "Loops lose Calcium" (used in treating hypercalcemia) [3]. * **Thiazides:** "Thiazides take Calcium" (reabsorb it back into the blood; used in treating hypercalciuria) [3].

Q: What is the mechanism of action of furosemide in left ventricular failure (LVF)?

Inhibitor of Na-K-Cl ion symporter. **Mechanism of Action:** Furosemide is a potent **Loop Diuretic**. Its primary mechanism involves the inhibition of the **Naⁱ-Kⁱ-2Clⁱ symporter (NKCC2)** [1] located in the luminal membrane of the **Thick Ascending Limb (TAL)** of the Henle’s loop [2]. By blocking this transporter, it prevents the reabsorption of these electrolytes, leading to profound diuresis and natriuresis [3]. **Role in Left Ventricular Failure (LVF):** In acute LVF (Pulmonary Edema), furosemide acts via two distinct phases [4]: 1. **Immediate Effect (Vascular):** It causes rapid **venodilation** (mediated by prostaglandins), which increases venous capacitance and decreases preload. This provides symptomatic relief even before the onset of diuresis. 2. **Delayed Effect (Renal):** It reduces fluid overload through diuresis, further decreasing the workload on the failing heart. **Analysis of Incorrect Options:** * **B. Aldosterone antagonist:** This describes **Spironolactone** or Eplerenone, which act on the distal tubule and collecting ducts. * **C. Mercurial derivative:** These are obsolete diuretics (e.g., Mersalyl) rarely used today due to toxicity. * **D. Carbonic anhydrase inhibitor:** This describes **Acetazolamide**, which acts on the proximal convoluted tubule and is primarily used for glaucoma or altitude sickness, not LVF [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Action:** Thick Ascending Limb (TAL) – the "diluting segment." * **Side Effects (The "Hypo"s):** Hypokalemia, Hypomagnesemia, Hypocalcemia (Loop loses Calcium), and Hyperuricemia. * **Ototoxicity:** Furosemide can cause dose-dependent hearing loss, especially when combined with aminoglycosides [2]. * **Drug of Choice:** Furosemide is the DOC for **Acute Pulmonary Edema** and edema associated with CHF, Cirrhosis, and Renal failure [4].

Question 1

Which diuretic can be used in renal failure?

Accepted Answer

Furosemide

Answer

Chlorothiazide

Answer

Mannitol

Answer

Chlorthalidone

Question 2

Which of the following side effects is associated with Spironolactone?

Accepted Answer

Hyperkalemia

Answer

Alkalosis

Answer

Hirsutism

Answer

Hyperglycemia

Question 3

A 64-year-old man with heart failure is recently started on 80 mg/day of furosemide. He now feels weak and tired, but notes that his heart failure symptoms have improved. There is no change in his urine output and he gets a good diuretic response every time he takes his furosemide. Which are the characteristic ECG findings?

Accepted Answer

lengthened QU interval

Answer

shortened PR interval

Answer

lengthened PR interval

Answer

shortening of the QT interval

Question 4

Which of the following drugs prevents renal stones?

Accepted Answer

Acetazolamide

Answer

Hydrochlorothiazide

Answer

Mannitol

Answer

Furosemide

Question 5

What is the mechanism of action of furosemide in left ventricular failure (LVF)?

Accepted Answer

Inhibitor of Na-K-Cl ion symporter

Answer

Aldosterone antagonist

Answer

Mercurial derivative

Answer

Carbonic anhydrase inhibitor

Diuretics — MCQs

Diuretics — MCQs

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