Combination Diuretic Therapy — MCQs

10 questions

A 65-year-old man with congestive heart failure presents with worsening bilateral pitting edema. What is the most appropriate next step in management?

Which diuretic acts on the loop of Henle?

All of the following diuretics increase K+ excretion EXCEPT:

A 45-year-old man with chronic liver disease presents with ascites and severe edema. Which diuretic combination is most suitable to manage his condition?

In which segment of the nephron does ethacrynic acid exert its diuretic action?

Which of the following drugs decreases free water clearance?

All the following adverse effects can be caused by Loop Diuretics EXCEPT -

Which electrolyte shows the most significant increase in urinary excretion within 24 hours of initiating thiazide diuretic therapy for hypertension?

Thiazides and loop diuretics both have opposite action on which of the following ions ?

Q10

Which diuretic is most likely to cause hyponatremia by impairing free water excretion?

Combination Diuretic Therapy Indian Medical PG Practice Questions and MCQs

Question 1: A 65-year-old man with congestive heart failure presents with worsening bilateral pitting edema. What is the most appropriate next step in management?

A. Increase diuretic dose (Correct Answer)
B. Add beta-blocker
C. Start corticosteroids
D. Prescribe ACE inhibitor

Explanation: ***Increase diuretic dose*** - Worsening **pitting edema** in a patient with **congestive heart failure** indicates fluid overload, and increasing the diuretic dose is the most direct and effective treatment [1]. - This aims to **reduce fluid retention** and alleviate symptoms like edema and congestion, improving the patient's hemodynamic status [1]. *Add beta-blocker* - Beta-blockers are crucial for **long-term management** of heart failure by improving cardiac function and survival, but they are typically initiated slowly in stable patients. - Adding a beta-blocker acutely in a patient with worsening fluid overload can exacerbate symptoms and is generally **contraindicated** if the patient is not euvolemic. *Start corticosteroids* - **Corticosteroids** have powerful **anti-inflammatory** and immunosuppressive effects but are not indicated for the management of fluid overload in heart failure [1]. - They can actually cause **sodium and fluid retention**, which would worsen the patient's edema and heart failure symptoms [1]. *Prescribe ACE inhibitor* - **ACE inhibitors** are foundational in heart failure therapy for reducing afterload and remodeling, but they do not directly address acute fluid overload [2]. - While beneficial for long-term management, initiating or increasing an ACE inhibitor would not be the most appropriate immediate step for acute worsening edema [2].

Question 2: Which diuretic acts on the loop of Henle?

A. Amiloride
B. Thiazides
C. Spironolactone
D. Furosemide (Correct Answer)

Explanation: ***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.

Question 3: All of the following diuretics increase K+ excretion EXCEPT:

A. Acetazolamide
B. Triamterene (Correct Answer)
C. Thiazide
D. Furosemide

Explanation: ***Triamterene*** - **Triamterene** is a **potassium-sparing diuretic** that blocks epithelial sodium channels (ENaC) in the collecting duct, thereby reducing sodium reabsorption and potassium secretion. - Unlike most other diuretics, it causes **decreased K+ excretion** and can lead to hyperkalemia. *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** that acts in the proximal tubule, inhibiting bicarbonate reabsorption. - This leads to increased delivery of sodium and bicarbonate to the collecting duct, which enhances **potassium secretion** and increases K+ excretion. *Thiazide* - **Thiazide diuretics** (e.g., hydrochlorothiazide) act by inhibiting the Na+/Cl- cotransporter in the **distal convoluted tubule**. - This increases the delivery of sodium to the collecting duct, which stimulates the exchange of sodium for **potassium**, leading to increased K+ excretion and hypokalemia. *Furosemide* - **Furosemide** is a **loop diuretic** that inhibits the Na+/K+/2Cl- cotransporter in the **thick ascending limb of the loop of Henle**. - This prevents the reabsorption of these ions, leading to increased delivery of sodium to the collecting duct, which promotes **potassium secretion** and increased K+ excretion.

Question 4: A 45-year-old man with chronic liver disease presents with ascites and severe edema. Which diuretic combination is most suitable to manage his condition?

A. Acetazolamide and Mannitol
B. Spironolactone and Furosemide (Correct Answer)
C. Metolazone and Torsemide
D. Hydrochlorothiazide and Amiloride

Explanation: ***Spironolactone and Furosemide*** - **Spironolactone**, an **aldosterone antagonist**, is crucial because **secondary hyperaldosteronism** often contributes to sodium and water retention in patients with chronic liver disease and ascites. - **Furosemide**, a **loop diuretic**, provides potent diuresis by inhibiting sodium reabsorption in the **thick ascending limb of the loop of Henle**, effectively reducing fluid overload. *Acetazolamide and Mannitol* - **Acetazolamide**, a **carbonic anhydrase inhibitor**, has a relatively weak diuretic effect and is not typically used for significant ascites due to chronic liver disease. - **Mannitol**, an **osmotic diuretic**, is primarily used for cerebral edema or acute renal failure, not for chronic fluid retention in liver disease, as it can worsen volume status. *Metolazone and Torsemide* - **Metolazone**, a **thiazide-like diuretic**, can be effective in combination with loop diuretics for refractory edema but is not the first-line combination for initial management of ascites in chronic liver disease. - **Torsemide** is a loop diuretic, similar to furosemide, but typically not combined with metolazone as a primary strategy without prior trials of spironolactone and a loop diuretic. *Hydrochlorothiazide and Amiloride* - **Hydrochlorothiazide**, a **thiazide diuretic**, is less potent than loop diuretics and generally less effective in patients with advanced liver disease and significant ascites. - **Amiloride**, a **potassium-sparing diuretic**, is weaker than spironolactone and does not block aldosterone, making it less effective in combating the pathophysiology of ascites in liver disease.

Question 5: In which segment of the nephron does ethacrynic acid exert its diuretic action?

A. Proximal convoluted tubule
B. Collecting duct
C. Distal convoluted tubule
D. Thick ascending limb of loop of Henle (Correct Answer)

Explanation: ***Thick ascending limb of loop of Henle*** - Ethacrynic acid is a **loop diuretic** that acts by inhibiting the **Na+-K+-2Cl- cotransporter** (NKCC2) in the luminal membrane of the thick ascending limb. - This inhibition prevents the reabsorption of ions, leading to increased excretion of water, sodium, chloride, and potassium. *Proximal convoluted tubule* - The proximal convoluted tubule is the primary site of reabsorption of most filtered substances, but loop diuretics like ethacrynic acid do not primarily act here. - Carbonic anhydrase inhibitors and SGLT2 inhibitors are examples of diuretics that exert their effects in this segment. *Collecting duct* - The collecting duct is the site where aldosterone antagonists (e.g., spironolactone) and epithelial sodium channel (ENaC) inhibitors (e.g., amiloride, triamterene) exert their diuretic effects. - Its primary role involves fine-tuning water reabsorption under the influence of ADH and regulating potassium excretion. *Distal convoluted tubule* - Thiazide diuretics primarily act in the distal convoluted tubule by inhibiting the **Na+-Cl- cotransporter** (NCC). - This segment is responsible for further diluting the urine and reabsorbing a small percentage of filtered sodium and chloride.

Question 6: Which of the following drugs decreases free water clearance?

A. Vincristine (Correct Answer)
B. Vinblastine
C. Chlorpropamide
D. Furosemide

Explanation: ***Vincristine*** - **Vincristine** is a chemotherapeutic agent (vinca alkaloid) that commonly causes **syndrome of inappropriate antidiuretic hormone secretion (SIADH)**. - SIADH leads to **excessive ADH secretion**, causing increased water reabsorption in the collecting ducts. - This results in **decreased free water clearance**, hyponatremia, and concentrated urine with low serum osmolality [2]. *Furosemide* - **Furosemide** is a loop diuretic that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle. - By reducing solute reabsorption, it impairs the medullary concentration gradient [2]. - This leads to impaired urinary concentration and **increased free water clearance** (dilute urine) [2]. *Vinblastine* - **Vinblastine** is another vinca alkaloid that can also cause SIADH, similar to vincristine. - However, vincristine is more commonly associated with SIADH than vinblastine. *Chlorpropamide* - **Chlorpropamide** is a first-generation sulfonylurea that can potentiate ADH action at the collecting duct [1]. - This leads to increased water reabsorption and decreased free water clearance [1]. - However, this effect is less clinically significant compared to SIADH-inducing drugs.

Question 7: All the following adverse effects can be caused by Loop Diuretics EXCEPT -

A. Hypomagnesemia
B. Hypercalcemia (Correct Answer)
C. Hyperuricemia
D. Hyperglycemia

Explanation: ***Hypercalcemia*** - Loop diuretics inhibit the reabsorption of calcium in the thick ascending limb of the loop of Henle, leading to **increased urinary calcium excretion** and, consequently, **hypocalcemia** [2], [3]. - Therefore, loop diuretics actively decrease calcium levels, so hypercalcemia is not an adverse effect. *Hypomagnesemia* - Loop diuretics interfere with magnesium reabsorption in the thick ascending limb, which can lead to **increased urinary excretion of magnesium** and subsequently cause **hypomagnesemia** [1], [2]. - This effect is clinically significant as it can exacerbate other electrolyte imbalances or cause symptoms like muscle weakness or arrhythmias. *Hyperuricemia* - Loop diuretics can lead to **hyperuricemia** by competing with uric acid for secretion into the renal tubule and by increasing its reabsorption, thereby decreasing its excretion [1]. - This can precipitate or worsen gout, especially in susceptible individuals [1]. *Hyperglycemia* - Loop diuretics, like thiazide diuretics, can cause **hyperglycemia** by impairing insulin secretion and increasing peripheral insulin resistance. - This effect is more pronounced with higher doses and prolonged use, potentially worsening glycemic control in diabetic patients or unmasking latent diabetes.

Question 8: Which electrolyte shows the most significant increase in urinary excretion within 24 hours of initiating thiazide diuretic therapy for hypertension?

A. Sodium (Correct Answer)
B. Potassium
C. Magnesium
D. Calcium

Explanation: ***Sodium*** - Thiazide diuretics primarily act on the **distal convoluted tubule** by inhibiting the **Na+/Cl- cotransporter**, leading to increased excretion of **sodium** and water [1]. - The initial and most significant pharmacological effect of thiazides is to promote **natriuresis**, removing excess sodium from the body [2]. - Within **24 hours**, sodium excretion shows the most pronounced increase, which is the primary mechanism for blood pressure reduction [2]. *Potassium* - While thiazides do cause **potassium excretion**, this effect is less significant than sodium excretion initially and is partly due to increased flow to the collecting duct and elevated aldosterone levels [2]. - Hypokalemia is a known side effect of long-term thiazide use, but the **immediate increase in urinary sodium** is more pronounced. *Magnesium* - Thiazide diuretics are known to cause **increased urinary excretion of magnesium**, which can lead to hypomagnesemia with chronic use [3]. - However, the initial increase in magnesium excretion is generally **less pronounced** compared to sodium excretion within the first 24 hours of therapy. *Calcium* - Uniquely among diuretics, thiazides **decrease** urinary calcium excretion, promoting calcium retention and reabsorption in the distal tubule [1], [3]. - This is why thiazides are sometimes used therapeutically in **hypercalciuric nephrolithiasis** and can cause hypercalcemia as a side effect. - Calcium excretion is **reduced**, not increased, making this the opposite of the correct answer.

Question 9: Thiazides and loop diuretics both have opposite action on which of the following ions ?

A. Potassium
B. Sodium
C. Chloride
D. Calcium (Correct Answer)

Explanation: ***Calcium*** - Thiazide diuretics **increase calcium reabsorption** in the distal convoluted tubule, leading to decreased urinary calcium excretion. - Loop diuretics **decrease calcium reabsorption** in the thick ascending limb of the loop of Henle, resulting in increased urinary calcium excretion. *Potassium* - Both thiazide and loop diuretics can cause **hypokalemia** by increasing potassium excretion in the urine. - This is due to increased sodium delivery to the collecting duct, which stimulates potassium secretion. *Sodium* - Both thiazide and loop diuretics inhibit sodium reabsorption at different sites in the nephron, leading to **increased urinary sodium excretion** (natriuresis). - This is their primary mechanism of action for diuresis. *Chloride* - Both thiazide and loop diuretics inhibit **chloride reabsorption** as they block specific sodium-chloride cotransporters. - Thiazides inhibit the Na-Cl cotransporter in the DCT, while loop diuretics inhibit the Na-K-2Cl cotransporter in the thick ascending limb.

Question 10: 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

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