Diuretics Practice Questions

Q: A 32-year-old male patient is treated for hypertension with thiazides. Which of the following adverse effects can occur in this patient?

Impotence. **Explanation:** Thiazide diuretics (e.g., Hydrochlorothiazide, Chlorthalidone) are first-line antihypertensive agents, but they are associated with several metabolic and systemic side effects. **Why Impotence is Correct:** Sexual dysfunction, specifically **erectile dysfunction (impotence)**, is a well-documented side effect of thiazide diuretics. While the exact mechanism is multifactorial, it is thought to involve a decrease in peripheral vascular resistance and a reduction in zinc levels, which is essential for testosterone production. In clinical trials, thiazides are more frequently associated with impotence compared to other antihypertensives like ACE inhibitors or Calcium Channel Blockers. **Analysis of Incorrect Options:** * **A. Hyperkalemic paralysis:** Thiazides inhibit the $Na^+/Cl^-$ symporter in the distal convoluted tubule, increasing sodium delivery to the collecting ducts. This promotes potassium excretion, leading to **hypokalemia**, not hyperkalemia. * **B. Hypouricemia:** Thiazides compete with uric acid for the organic acid secretory secretory pump in the proximal tubule. This leads to decreased uric acid excretion, resulting in **hyperuricemia**, which can precipitate gout. * **C. Hypolipidemia:** Thiazides can cause a transient increase in serum cholesterol and LDL levels (**hyperlipidemia**), though this effect often diminishes with long-term therapy. **High-Yield Clinical Pearls for NEET-PG:** * **The "Hyper" Rule:** Thiazides cause **Hyper**glycemia, **Hyper**uricemia, **Hyper**lipidemia, and **Hyper**calcemia (useful in treating idiopathic hypercalciuria/kidney stones). * **The "Hypo" Rule:** Thiazides cause **Hypo**kalemia, **Hypo**natremia, and **Hypo**magnesemia. * **Chlorthalidone** is currently preferred over Hydrochlorothiazide due to its longer half-life and superior evidence in reducing cardiovascular events.

Q: Which of the following diuretics keeps urine isotonic?

Loop diuretics. **Explanation:** The correct answer is **Loop Diuretics** (e.g., Furosemide). This occurs because loop diuretics inhibit the **Na⁺-K⁺-2Cl⁻ symporter** in the Thick Ascending Limb (TAL) of the Loop of Henle. **Why Loop Diuretics keep urine isotonic:** The TAL is responsible for reabsorbing solutes without water, which creates the **medullary osmotic gradient**. This gradient is essential for both concentrating urine (via ADH) and diluting urine. By blocking solute reabsorption in this segment, loop diuretics abolish the medullary hypertonicity. Consequently, the kidney loses its ability to concentrate or dilute urine, resulting in the excretion of urine that has the same osmolality as plasma (~300 mOsm/L), a phenomenon known as **isosthenuria**. **Why other options are incorrect:** * **Thiazide Diuretics:** These act on the Distal Convoluted Tubule (DCT). They interfere with the kidney’s ability to dilute urine but do **not** affect the medullary gradient. Therefore, the urine remains concentrated (hypertonic) relative to the initial filtrate. * **Carbonic Anhydrase Inhibitors:** These act on the Proximal Convoluted Tubule. While they increase bicarbonate and sodium excretion, they do not disrupt the primary concentrating mechanism of the medulla, thus not resulting in strictly isotonic urine. **High-Yield Clinical Pearls for NEET-PG:** * **"High Ceiling" Diuretics:** Loop diuretics are called this because they have a dose-dependent response with a very high maximal efficacy. * **Calcium Effect:** Loop diuretics cause **hypocalcemia** ("Loops Lose Calcium"), whereas Thiazides cause **hypercalcemia**. * **Drug of Choice:** Loop diuretics are the DOC for acute pulmonary edema and generalized edema (CHF, Nephrotic syndrome).

Q: What is the longest-acting thiazide diuretic?

Chlorthalidone. **Chlorthalidone** is the longest-acting diuretic among the options provided [1]. Although it is chemically a "thiazide-like" diuretic (lacking the benzothiadiazine ring) [2, 3], it shares the same mechanism of action: inhibiting the **Na⁺-Cl⁻ symporter** in the Distal Convoluted Tubule (DCT) [1, 2].**Why Chlorthalidone is the correct answer:**The prolonged duration of action of Chlorthalidone (**48–72 hours**) [2] is primarily due to its high affinity for **carbonic anhydrase** in erythrocytes. This leads to extensive binding within red blood cells, creating a large reservoir that is slowly released into the plasma and delivered to the kidneys. Because of this long half-life, it provides superior 24-hour blood pressure control compared to Hydrochlorothiazide [1].**Analysis of Incorrect Options:** * **A. Chlorthiazide:** This is the prototype thiazide but has a very short half-life (approx. 1.5–2 hours) and low lipid solubility [2]. * **C. Indapamide:** A thiazide-like diuretic with a duration of action of about 24 hours [2, 3]. It is notable for its dual action (diuretic + vasodilation) and is often preferred in patients with renal impairment. * **D. Metolazone:** A potent thiazide-like diuretic with a duration of action of about 12–24 hours [2, 3]. It is unique because it remains effective even when the GFR is low (<30 mL/min).**High-Yield Clinical Pearls for NEET-PG:** * **Potency:** Chlorthalidone is roughly 1.5 to 2 times more potent than Hydrochlorothiazide. * **Drug of Choice:** Recent hypertension guidelines (like ACC/AHA) often prefer Chlorthalidone over other thiazides due to its proven reduction in cardiovascular events. * **Metabolic Side Effects:** All thiazides can cause the "Hyper" states: **Hyper**glycemia, **Hyper**lipidemia, **Hyper**uricemia, and **Hyper**calcemia; and "Hypo" states: **Hypo**kalemia, **Hypo**natremia, and **Hypo**magnesemia.

Q: Which is a safe diuretic in renal dysfunction?

Bumetanide. ### Explanation **Correct Answer: B. Bumetanide** **Why Bumetanide is the correct choice:** Bumetanide is a high-ceiling **Loop Diuretic**. Loop diuretics (including Furosemide and Torsemide) are the diuretics of choice in patients with renal dysfunction (GFR < 30 ml/min). Unlike other classes, loop diuretics maintain their efficacy even when the glomerular filtration rate (GFR) is significantly reduced. They act on the thick ascending limb of the Loop of Henle, which has a large capacity for sodium reabsorption, ensuring a potent natriuretic effect even in failing kidneys. **Why the other options are incorrect:** * **Mannitol (Osmotic Diuretic):** It is contraindicated in established anuria or severe renal failure. It expands extracellular fluid volume, which can lead to acute pulmonary edema and heart failure in patients who cannot excrete the fluid load. * **Chlorthalidone (Thiazide-like Diuretic):** Thiazides and related drugs generally lose their efficacy when the GFR falls below 30 ml/min (with the exception of Metolazone). They are not the preferred agents for fluid management in advanced renal impairment. * **Acetazolamide (Carbonic Anhydrase Inhibitor):** It is a weak diuretic that acts on the proximal tubule. It is avoided in renal failure as it can worsen metabolic acidosis (a common complication of uremia) and has a very limited diuretic effect. **High-Yield Clinical Pearls for NEET-PG:** * **Potency Ratio:** Bumetanide is roughly **40 times more potent** than Furosemide (1 mg Bumetanide ≈ 40 mg Furosemide). * **Metolazone Exception:** While most thiazides fail in renal impairment, **Metolazone** remains effective and is often combined with loop diuretics to overcome "diuretic resistance" (Sequential Nephron Blockade). * **Ototoxicity:** While all loop diuretics can cause ototoxicity, **Ethacrynic acid** is the most ototoxic, while Bumetanide is generally considered to have a lower risk compared to high-dose Furosemide.

Q: A 72-year-old woman with mild heart failure is treated overzealously with a thiazide diuretic. A few days later, the woman complains of muscle weakness, and laboratory tests demonstrate hypokalemia. Which of the following is most likely increased in this woman?

Plasma aldosterone. **Explanation:** The correct answer is **B. Plasma aldosterone**. **Mechanism of Action:** Thiazide diuretics inhibit the $Na^+/Cl^-$ symporter in the distal convoluted tubule, leading to increased excretion of sodium and water. Overzealous use causes **volume depletion** (hypovolemia). This reduction in effective circulating volume triggers the **Renin-Angiotensin-Aldosterone System (RAAS)**. Juxtaglomerular cells sense decreased renal perfusion and release renin, ultimately leading to elevated levels of **Aldosterone**. Aldosterone then acts on the collecting ducts to reabsorb sodium at the expense of secreting potassium and hydrogen ions, which explains the patient's hypokalemia and muscle weakness. **Analysis of Incorrect Options:** * **A. Serum $H^+$ concentration:** Thiazides cause **metabolic alkalosis** (contraction alkalosis and increased $H^+$ secretion in the collecting duct). Therefore, $H^+$ concentration decreases, and pH increases. * **C. Plasma sodium:** Thiazides are a common cause of **hyponatremia**. They promote sodium excretion while the compensatory ADH release (due to volume depletion) causes water retention, diluting serum sodium. * **D. Potassium retention:** Thiazides cause **potassium wasting** (hypokalemia) due to increased sodium delivery to the late distal tubule and high aldosterone levels, both of which drive $K^+$ secretion. **NEET-PG High-Yield Pearls:** * **Thiazide Side Effects (Hyper-GLUC):** Hyper**G**lycemia, Hyper**L**ipidemia, Hyper**U**ricemia, and Hyper**C**alcemia. * **Electrolyte Profile:** Hypokalemic metabolic alkalosis + Hyponatremia. * **Clinical Note:** Unlike Loop diuretics (which cause hypocalcemia), Thiazides decrease urinary calcium and are used in treating **calcium nephrolithiasis**.

Q: A 55-year-old man with congestive heart failure is noted to be taking furosemide each day. Which of the following is most likely to be found in the serum?

Decreased potassium level. **Explanation:** **Mechanism of Action (The Correct Answer):** Furosemide is a high-ceiling **loop diuretic** that inhibits the **Na+/K+/2Cl- symporter** in the Thick Ascending Limb (TAL) of the Henle’s loop. By blocking this transporter, it increases the delivery of sodium to the distal convoluted tubule and collecting duct. In the collecting duct, the increased sodium load promotes sodium reabsorption in exchange for **potassium (K+) and hydrogen (H+) ions** via the action of aldosterone. This leads to increased urinary excretion of potassium, resulting in **hypokalemia** (decreased serum potassium levels). **Analysis of Incorrect Options:** * **A. Decreased uric acid level:** Incorrect. Loop diuretics cause **hyperuricemia** (elevated uric acid). This occurs because diuretics cause volume depletion, leading to increased proximal tubular reabsorption of uric acid, and they compete with uric acid for the organic acid secretory pathway in the kidney. * **B. Low bicarbonate level:** Incorrect. Furosemide causes **contraction alkalosis**, which is characterized by an **increase** in serum bicarbonate levels due to the loss of H+ ions and volume contraction. * **D. Elevated magnesium level:** Incorrect. The Na+/K+/2Cl- symporter normally creates a positive lumen potential that drives the paracellular reabsorption of divalent cations. By inhibiting this, furosemide causes **hypomagnesemia** and **hypocalcemia**. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Loop Diuretic Side Effects:** "OH DANG!" (**O**totoxicity, **H**ypokalemia, **D**ehydration, **A**llergy (sulfa), **N**ephritis, **G**out). * **Calcium Handling:** Unlike Thiazides (which cause hypercalcemia), Loop diuretics cause **hypocalcemia** ("Loops Lose Calcium"). * **Drug of Choice:** Furosemide is the drug of choice for acute pulmonary edema in CHF due to its rapid-acting diuretic and vasodilator properties.

Question 1

Spironolactone is used in the treatment of patients with Conn's syndrome. Which of the following is the most important adverse reaction of spironolactone therapy?

Accepted Answer

Antiandrogen effects

Answer

Cardiac arrhythmia

Answer

Dehydration

Answer

Hyperkalemia

Question 2

A 32-year-old male patient is treated for hypertension with thiazides. Which of the following adverse effects can occur in this patient?

Accepted Answer

Impotence

Answer

Hyperkalemic paralysis

Answer

Hypouricemia

Answer

Hypolipidemia

Question 3

Which of the following diuretics keeps urine isotonic?

Accepted Answer

Loop diuretics

Answer

Thiazide diuretics

Answer

Carbonic anhydrase inhibitors

Answer

None of the above

Question 4

What is the longest-acting thiazide diuretic?

Accepted Answer

Chlorthalidone

Answer

Chlorthiazide

Answer

Indapamide

Answer

Metolazone

Question 5

Which of the following diuretics will continue to induce significant diuresis after return of blood volume to normal levels?

Accepted Answer

furosemide

Answer

hydrochlorothiazide

Answer

spironolactone

Answer

triamterene

Question 6

An 82-year-old man with congestive heart failure and a creatinine clearance (CrCl) of 17 mL/min requires a diuretic for the treatment of peripheral edema. Which of the following diuretics would be most appropriate in this patient?

Accepted Answer

Furosemide

Answer

Hydrochlorothiazide

Answer

Indapamide

Answer

Spironolactone

Question 7

Which is a safe diuretic in renal dysfunction?

Accepted Answer

Bumetanide

Answer

Mannitol

Answer

Chlorthalidone

Answer

Acetazolamide

Question 8

K+ secretion from the loop of Henle is decreased by which of the following medications?

Accepted Answer

Spironolactone

Answer

Furosemide

Answer

Thiazide

Answer

Acetazolamide

Question 9

A 72-year-old woman with mild heart failure is treated overzealously with a thiazide diuretic. A few days later, the woman complains of muscle weakness, and laboratory tests demonstrate hypokalemia. Which of the following is most likely increased in this woman?

Accepted Answer

Plasma aldosterone

Answer

Serum H+ concentration

Answer

Plasma sodium

Answer

Potassium retention

Question 10

A 55-year-old man with congestive heart failure is noted to be taking furosemide each day. Which of the following is most likely to be found in the serum?

Accepted Answer

Decreased potassium level

Answer

Decreased uric acid level

Answer

Low bicarbonate level

Answer

Elevated magnesium level

Diuretics — MCQs

Diuretics — MCQs

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