Diuretics — MCQs
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A 72-year-old male with chronic kidney disease has elevated serum potassium levels. Which drug is likely contributing to his hyperkalemia?
Which of the following drugs is used in SIADH?
Gitelman's syndrome resembles the effects of which of the following drugs?
What is the most clinically significant electrolyte disturbance caused by loop diuretics?
Mannitol is most commonly used for which of the following conditions?
Which diuretic inhibits the Na+-K+-2Cl- symporter in the thick ascending limb of the loop of Henle?
Which diuretic is most likely to cause hyponatremia by impairing free water excretion?
How do thiazides cause hypercalcemia?
Which of the following is not a side effect of thiazide diuretics?
Which diuretic is known to cause the maximum potassium loss?
Diuretics Indian Medical PG Practice Questions and MCQs
Question 191: A 72-year-old male with chronic kidney disease has elevated serum potassium levels. Which drug is likely contributing to his hyperkalemia?
- A. Furosemide
- B. Hydrochlorothiazide
- C. Spironolactone (Correct Answer)
- D. Amlodipine
Explanation: **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.
Question 192: Which of the following drugs is used in SIADH?
- A. Desmopressin
- B. Von Willebrand factor
- C. Tolvaptan (Correct Answer)
- D. Terlipressin
Explanation: ***Tolvaptan*** - **Tolvaptan** is an **oral vasopressin V2-receptor antagonist** that promotes water excretion without affecting sodium, making it effective for **hyponatremia** associated with SIADH [1]. - It works by blocking the action of **antidiuretic hormone (ADH)** at the renal collecting ducts, increasing free water clearance and thus raising serum sodium levels [1].*Desmopressin* - **Desmopressin** is a synthetic analog of **ADH (vasopressin)**, which acts as a V2 receptor agonist [2]. - It is used to **increase water reabsorption** and is therefore contraindicated in SIADH, where ADH levels are already inappropriately high [1].*Von Willebrand factor* - **Von Willebrand factor** is a protein primarily involved in **hemostasis** and is used to treat **Von Willebrand disease** and **hemophilia A**. - It has no role in the management of SIADH, which is a disorder of water balance.*Terlipressin* - **Terlipressin** is a vasopressin analog that acts as a **V1 receptor agonist**, primarily causing splanchnic vasoconstriction. - It is used to treat **esophageal variceal bleeding** and **hepatorenal syndrome**, but it is not indicated for SIADH.
Question 193: Gitelman's syndrome resembles the effects of which of the following drugs?
- A. Thiazide diuretics (Correct Answer)
- B. Loop diuretics (Furosemide)
- C. Potassium-sparing diuretics (Spironolactone)
- D. Carbonic anhydrase inhibitors (Acetazolamide)
Explanation: ***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.
Question 194: What is the most clinically significant electrolyte disturbance caused by loop diuretics?
- A. Hypokalemia (Correct Answer)
- B. Dehydration
- C. Hyperkalemia
- D. Fluid retention
Explanation: ***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 195: Mannitol is most commonly used for which of the following conditions?
- A. Impending renal failure
- B. Glaucoma
- C. Raised intracranial tension (ICT) (Correct Answer)
- D. Pulmonary edema
Explanation: ***Raised intracranial tension (ICT)*** - **Mannitol** is an osmotic diuretic that creates an osmotic gradient, drawing water from the **brain parenchyma** into the vascular space, thereby reducing brain volume and **intracranial pressure**. - It is particularly effective in acute settings for managing **cerebral edema** associated with trauma, stroke, or tumors. *Glaucoma* - While mannitol can reduce **intraocular pressure** in acute glaucoma, it is not the most common or first-line treatment. - Other medications like topical beta-blockers, alpha-agonists, and prostaglandin analogs are typically preferred for long-term management and acute relief. *Impending renal failure* - **Mannitol** can induce osmosis of fluid, which could increase urine output. However, it is **contraindicated** in established **renal failure** due to the risk of exacerbating fluid overload and electrolyte imbalances. - Its use in impending renal failure is limited and typically reserved for specific situations like preventing acute kidney injury during cardiac surgery, and it is not a primary treatment. *Pulmonary edema* - **Mannitol** can increase **intravascular volume** as it draws fluid from interstitial spaces, which can worsen **pulmonary edema**, especially in patients with heart failure. - Diuretics like furosemide (loop diuretics) are the preferred treatment for pulmonary edema.
Question 196: Which diuretic inhibits the Na+-K+-2Cl- symporter in the thick ascending limb of the loop of Henle?
- A. Thiazides
- B. Furosemide (Correct Answer)
- C. Amiloride
- D. Acetazolamide
Explanation: ***Furosemide*** - Furosemide is a **loop diuretic** that acts by inhibiting the **Na+-K+-2Cl- symporter** (NKCC2) in the luminal membrane of the epithelial cells in the thick ascending limb of the **loop of Henle** [1], [2]. - This inhibition prevents the reabsorption of sodium, potassium, and chloride ions, leading to increased excretion of these ions and water [1]. *Thiazides* - Thiazide diuretics, such as **hydrochlorothiazide**, primarily act on the **distal convoluted tubule** [4]. - They inhibit the **Na+-Cl- cotransporter**, not the Na+-K+-2Cl- symporter [4]. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor** that primarily acts in the **proximal convoluted tubule** [3]. - It inhibits the reabsorption of bicarbonate, leading to increased excretion of bicarbonate, sodium, and water [3]. *Amiloride* - Amiloride is a **potassium-sparing diuretic** that acts on the **collecting duct**. - It inhibits the **epithelial sodium channel (ENaC)**, leading to reduced sodium reabsorption and potassium secretion.
Question 197: Which diuretic is most likely to cause hyponatremia by impairing free water excretion?
- A. Loop diuretics
- B. Acetazolamide
- C. Amiloride
- D. Thiazide diuretics (Correct Answer)
Explanation: ***Thiazide diuretics*** - **Thiazide diuretics** inhibit the **Na-Cl cotransporter in the distal convoluted tubule (DCT)**, impairing the kidney's ability to dilute urine and excrete free water - This impaired urinary dilution leads to **water retention relative to sodium**, resulting in **dilutional hyponatremia** - **Most common in elderly patients**, those on low-salt diets, or with pre-existing volume depletion - **Mechanism**: By blocking sodium reabsorption in the DCT (a key site for urinary dilution), thiazides prevent the generation of free water, leading to hyponatremia when water intake continues *Loop diuretics* - **Loop diuretics** inhibit the **Na-K-2Cl cotransporter in the thick ascending limb of Henle**, causing significant diuresis - They impair the medullary concentration gradient, **enhancing free water excretion** - **Less likely to cause hyponatremia** compared to thiazides because they promote rather than impair free water clearance - When hyponatremia occurs with loop diuretics, it's usually due to concurrent SIADH or excessive free water intake *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** acting primarily on the **proximal tubule** - Causes **bicarbonate and sodium excretion**, leading to mild diuresis - Main side effect is **metabolic acidosis** (type 2 RTA) - **Does not significantly impair free water excretion**, making hyponatremia uncommon *Amiloride* - **Amiloride** is a **potassium-sparing diuretic** that blocks **epithelial sodium channels (ENaC) in the collecting duct** - Weak diuretic effect, primarily used to prevent potassium loss - **Does not impair urinary dilution mechanisms**, so hyponatremia is rare - Main concern is **hyperkalemia**, especially with ACE inhibitors or in renal insufficiency
Question 198: How do thiazides cause hypercalcemia?
- A. Decreased calcium excretion (Correct Answer)
- B. Increased parathyroid hormone secretion
- C. Decreased calcitonin secretion
- D. Increased calcium absorption
Explanation: ***Decreased calcium excretion*** - Thiazides inhibit the **Na-Cl co-transporter** in the **distal convoluted tubule**, leading to increased reabsorption of calcium [1], [2]. - This increased reabsorption of calcium is mediated by a low intracellular sodium concentration, which enhances the activity of the **Na+/Ca2+ exchanger** on the basolateral membrane [1]. *Increased parathyroid hormone secretion* - Thiazides **do not directly stimulate** parathyroid hormone (PTH) secretion; instead, they *decrease* calcium excretion, which would typically *lower* PTH levels through negative feedback. - Elevated PTH would lead to increased bone resorption and kidney calcium reabsorption, but this is not the **primary mechanism** for thiazide-induced hypercalcemia [2]. *Decreased calcitonin secretion* - **Calcitonin** is a hormone that *lowers* blood calcium levels, and its decrease would theoretically contribute to hypercalcemia. - However, thiazides have **no direct effect** on calcitonin secretion, making this an unlikely primary mechanism. *Increased calcium absorption* - While increased calcium absorption from the gut can contribute to hypercalcemia, thiazides do **not directly increase intestinal calcium absorption**. - Their primary action for influencing calcium levels is within the **kidney**, specifically on reabsorption, not absorption from the GI tract [1], [2].
Question 199: Which of the following is not a side effect of thiazide diuretics?
- A. Hypokalemia
- B. Impotence
- C. Hypocalcemia (Correct Answer)
- D. Hepatic coma
Explanation: ***Hypocalcemia*** - Thiazide diuretics are known to cause **hypercalcemia** (increased calcium levels) by enhancing calcium reabsorption in the distal convoluted tubule. - Therefore, hypocalcemia is not a direct side effect of thiazide diuretics. *Hypokalemia* - Thiazide diuretics inhibit the Na+/Cl- cotransporter in the **distal convoluted tubule**, leading to increased sodium delivery to the collecting duct. - This increased sodium delivery promotes potassium secretion and can result in **hypokalemia**. *Hepatic coma* - Thiazide diuretics can exacerbate or precipitate **hepatic encephalopathy** and coma in patients with pre-existing liver disease. - This is primarily due to diuretic-induced **hypokalemia** and metabolic alkalosis, which increase renal ammonia production. *Impotence* - Thiazide diuretics, particularly at higher doses, have been associated with various sexual side effects, including **erectile dysfunction (impotence)** in men. - While the exact mechanism is not fully understood, it is a recognized adverse effect.
Question 200: Which diuretic is known to cause the maximum potassium loss?
- A. Spironolactone
- B. Furosemide (Correct Answer)
- C. Thiazide diuretics
- D. Acetazolamide
Explanation: ***Furosemide*** - Furosemide is a **loop diuretic** that inhibits the Na-K-2Cl cotransporter in the **thick ascending limb of the loop of Henle**, leading to significant excretion of sodium, chloride, potassium, and water. - Its potent diuresis and impact on potassium reabsorption result in a **high risk of hypokalemia**. *Thiazide* - Thiazide diuretics inhibit the **Na-Cl cotransporter** in the **distal convoluted tubule**, causing moderate sodium and water excretion, and some potassium loss. - While they can cause hypokalemia, their effect on potassium excretion is generally **less pronounced than loop diuretics**. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor** that acts primarily in the **proximal tubule**, inhibiting bicarbonate reabsorption and leading to increased excretion of bicarbonate, sodium, potassium, and water. - The potassium loss is due to increased delivery of sodium to the collecting duct, leading to enhanced potassium secretion, but it is typically **less severe than with loop diuretics**. *Spironolactone* - Spironolactone is a **potassium-sparing diuretic** that acts as an **aldosterone antagonist** in the collecting duct, inhibiting sodium reabsorption and potassium secretion. - Instead of causing potassium loss, spironolactone actually **conserves potassium** and can lead to hyperkalemia.
Practice by Chapter
Carbonic Anhydrase Inhibitors
Practice Questions
Loop Diuretics
Practice Questions
Thiazide and Thiazide-Like Diuretics
Practice Questions
Potassium-Sparing Diuretics
Practice Questions
Carbonic Anhydrase Inhibitors
Practice Questions
Osmotic Diuretics
Practice Questions
Combination Diuretic Therapy
Practice Questions
Diuretics in Heart Failure
Practice Questions
Diuretics in Hypertension
Practice Questions
Diuretics in Renal Disorders
Practice Questions
Adverse Effects and Drug Interactions
Practice Questions
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