Diuretics Practice Questions

Q: Which of the following is a carbonic anhydrase inhibitor?

Acetazolamide. ***Acetazolamide*** - Acetazolamide is a classic example of a **carbonic anhydrase inhibitor**, primarily used as a diuretic and for managing **glaucoma** and **altitude sickness**. - It works by inhibiting the enzyme **carbonic anhydrase** in the **proximal renal tubule**, reducing bicarbonate reabsorption and thus promoting diuresis. *Hydrochlorothiazide* - Hydrochlorothiazide is a **thiazide diuretic** that acts on the **distal convoluted tubule** to inhibit the reabsorption of sodium and chloride. - It is not a carbonic anhydrase inhibitor. *Mannitol* - Mannitol is an **osmotic diuretic** that works in the **proximal tubule** and **descending limb of Henle's loop** by creating an osmotic gradient. - It is not a carbonic anhydrase inhibitor and functions by drawing water into the renal tubule, leading to increased urine output. *Furosemide* - Furosemide is a **loop diuretic** that acts on the **thick ascending limb of the loop of Henle** by inhibiting the Na+-K+-2Cl- cotransporter. - It is one of the most potent diuretics but does not inhibit carbonic anhydrase.

Q: Hydrochlorothiazide works by inhibiting

Na+ Cl pump in early DCT. ***Na+ Cl pump in early DCT*** - **Hydrochlorothiazide** is a **thiazide diuretic** that acts primarily on the **early distal convoluted tubule (DCT)**. - It inhibits the **sodium-chloride cotransporter (NCC)**, leading to increased excretion of sodium, chloride, and water. *Na+ Cl pump in late DCT* - The **late DCT** and collecting duct are primarily involved in fine-tuning sodium reabsorption, influenced by **aldosterone**, not the primary site of action for thiazides. - The **epithelial sodium channel (ENaC)** and Na+/K+-ATPase are more prominent here. *Na+ K+ 2Cl pump in descending limb of loop of Henle* - The **descending limb of the loop of Henle** is primarily permeable to water, with no active ion pumps like **Na+ K+ 2Cl pump**. - Its main function is to concentrate the urine by allowing water to move out. *Na+ K+ 2Cl pump in ascending limb of loop of Henle* - **Furosemide** and other **loop diuretics** act on the **Na+ K+ 2Cl cotransporter (NKCC2)** in the **thick ascending limb of the loop of Henle**, not hydrochlorothiazide. - Inhibition here prevents significant reabsorption of sodium, potassium, and chloride, leading to potent diuresis.

Q: Which one of the following is not a clinical use of spironolactone?

Pulmonary edema. ***Pulmonary edema*** - While spironolactone is a **diuretic**, its onset of action is relatively slow (days to weeks), making it unsuitable for the acute management of **pulmonary edema**, which requires rapid fluid removal. - For acute pulmonary edema, fast-acting loop diuretics like **furosemide** are preferred due to their potent and rapid diuresis. *Congestive heart failure* - Spironolactone is a **potassium-sparing diuretic** and an **aldosterone antagonist**, which improves outcomes in **congestive heart failure** by reducing fluid retention, myocardial fibrosis, and sympathetic activation. - It specifically helps in preventing **cardiac remodeling** and has been shown to reduce mortality in patients with heart failure. *Hypertension* - Spironolactone is used as an **adjunctive treatment for hypertension**, particularly in cases of **resistant hypertension** or when there is evidence of primary hyperaldosteronism. - It helps lower **blood pressure** by blocking aldosterone's effects, leading to increased sodium and water excretion. *To counteract hypokalemia due to thiazide diuretics* - As a **potassium-sparing diuretic**, spironolactone directly counteracts the **hypokalemia** (low potassium) that can be induced by other diuretics, such as **thiazide diuretics** and **loop diuretics**. - Its mechanism involves blocking **aldosterone receptors** in the collecting duct, reducing potassium secretion and sodium reabsorption.

Q: A patient is going skiing high in the Rockies and is given acetazolamide to protect against altitude sickness. Unfortunately, the patient is also a type 1 diabetic. He is admitted to the hospital in a worsening ketoacidosis. In which of the following cells has acetazolamide inhibited a reaction that has led to the severity of the metabolic acidosis?

Renal tubular cells. ***Renal tubular cells*** - Acetazolamide is a **carbonic anhydrase inhibitor**, primarily acting in the **proximal renal tubular cells** to block the enzyme carbonic anhydrase. - This inhibition prevents **bicarbonate (HCO₃⁻) reabsorption** in the proximal tubule, causing bicarbonate wasting in urine and resulting in **metabolic acidosis** (specifically type 2 renal tubular acidosis). - In this patient already suffering from **diabetic ketoacidosis** (DKA), which is itself a metabolic acidosis with low bicarbonate, the additional bicarbonate loss from acetazolamide **worsens the severity** of the acidosis. - This represents a clinically important drug-disease interaction. *Cells in the lens of the eye* - While carbonic anhydrase is present in the eye and acetazolamide can reduce **intraocular pressure** (used therapeutically for glaucoma), this mechanism is unrelated to systemic metabolic acidosis. - Inhibition here affects aqueous humor production but does not directly or significantly contribute to **acid-base balance** in the blood. *Liver cells* - The liver is crucial for metabolism and ammonia detoxification, but acetazolamide's primary action on acid-base balance is not directly through **hepatic carbonic anhydrase**. - Liver dysfunction can impact acid-base balance, but the liver is not the direct target or primary cause of acetazolamide-induced acidosis. *Immune system cells* - Carbonic anhydrase activity in **immune cells** is involved in processes like **pH regulation within phagosomes** and T-cell activation. - However, modulation of immune cell function by acetazolamide does not significantly contribute to its effect on systemic **metabolic acidosis**.

Q: Which of the following diuretics is contraindicated in Hepatic coma?

Acetazolamide. ***Acetazolamide*** - **Acetazolamide** inhibits carbonic anhydrase, leading to increased bicarbonate excretion and metabolic acidosis. In patients with **hepatic coma**, this can worsen the condition by impairing the liver's ability to convert ammonia to urea, leading to increased levels of **ionized ammonia** that can cross the blood-brain barrier. - The resulting **metabolic acidosis** can also interfere with the kidney's response to ammonia, further exacerbating the **hepatic encephalopathy**. *Bumetanide* - **Bumetanide** is a loop diuretic that acts on the **thick ascending limb of the loop of Henle** to inhibit sodium, potassium, and chloride reabsorption. - It does not directly exacerbate **hepatic encephalopathy** through metabolic acidosis in the same way as acetazolamide. *Furosemide* - **Furosemide** is a loop diuretic similar to bumetanide, acting on the **thick ascending limb** to promote diuresis. - While aggressive diuresis with furosemide in critical patients can sometimes lead to **volume depletion** and electrolyte imbalances that may indirectly affect liver function, it does not directly worsen **hepatic coma** by altering systemic acid-base balance and ammonia detoxification like acetazolamide. *Spironolactone* - **Spironolactone** is an **aldosterone antagonist** and a potassium-sparing diuretic, commonly used in liver cirrhosis with ascites. - It does not directly cause **metabolic acidosis** or increase ionized ammonia levels; in fact, by improving fluid balance, it can sometimes help manage complications of liver disease.

Q: What is the effect of thiazide diuretics on urinary calcium excretion?

Decrease excretion. ***Decrease excretion*** - Thiazide diuretics work by inhibiting the **sodium-chloride cotransporter (NCC)** in the **distal convoluted tubule** of the nephron. - This action leads to increased reabsorption of calcium in the distal tubule via **enhanced activity of the apical calcium channels (TRPV5)** and **basolateral Na+/Ca2+ exchanger (NCX1)**, thereby **decreasing urinary calcium excretion**. - This effect is clinically utilized in patients with **recurrent calcium kidney stones** and **hypercalciuria**. *Increase excretion* - Loop diuretics, like furosemide, block the **Na-K-2Cl cotransporter (NKCC2)** in the thick ascending limb of the loop of Henle, which is associated with **increased calcium excretion**. - Thiazide diuretics have the opposite effect on calcium handling compared to loop diuretics. *No effect* - This is incorrect because thiazide diuretics have a **well-documented and clinically significant effect** on calcium excretion. - The calcium-retaining effect is **consistent and predictable**, not absent. *Variable effect* - The effect of thiazides on calcium is **not variable** but rather **consistent and dose-dependent** in decreasing urinary calcium excretion. - This is a **primary pharmacological action**, not a variable or secondary effect.

Q: Side effects of oral carbonic anhydrase inhibitors include?

Paresthesia. ***Paresthesia*** - **Paresthesia** (tingling sensation, especially in fingers, toes, and perioral region) is one of the **most common side effects** of carbonic anhydrase inhibitors like acetazolamide - Occurs due to **systemic metabolic acidosis** and altered neuronal excitability from pH shifts and electrolyte changes - This symptom is so common that patients should be counseled about it before starting therapy *Hyperkalemia* - Carbonic anhydrase inhibitors cause **hypokalemia (potassium wasting)**, NOT hyperkalemia - Mechanism: Increased sodium delivery to distal tubule → increased Na-K exchange → urinary potassium loss - Although metabolic acidosis can shift potassium out of cells, the **diuretic effect predominates**, leading to net potassium loss *Insomnia* - **Not a recognized side effect** of carbonic anhydrase inhibitors - Patients may actually experience **fatigue or drowsiness** rather than insomnia - No direct pharmacological mechanism links carbonic anhydrase inhibition to sleep disturbances *Weight gain* - Carbonic anhydrase inhibitors have a **diuretic effect** causing fluid and sodium loss - Patients typically experience **weight loss or stable weight**, not weight gain - Weight gain is associated with fluid-retaining medications, which is the opposite effect of diuretics

Q: Loop and thiazide diuretics commonly cause clinically significant loss of:

Potassium. ***Potassium*** - Loop diuretics (e.g., furosemide) and thiazide diuretics (e.g., hydrochlorothiazide) inhibit sodium reabsorption in the renal tubules, leading to **increased urinary potassium excretion**. - This results in **hypokalemia**, a clinically significant side effect that requires monitoring and often necessitates **potassium supplementation** or the addition of **potassium-sparing diuretics** (e.g., spironolactone, amiloride). - Hypokalemia can cause muscle weakness, cardiac arrhythmias, and increased digitalis toxicity. *Sodium* - While diuretics do increase sodium excretion (their primary therapeutic mechanism), the question focuses on **clinically significant electrolyte loss** that requires intervention. - Sodium loss is the intended therapeutic effect for volume reduction, not typically considered a problematic "side effect." *Calcium* - **Loop diuretics** increase calcium excretion (useful in hypercalcemia treatment). - **Thiazide diuretics** actually decrease calcium excretion (can increase serum calcium, useful in osteoporosis). - The effects are variable depending on diuretic class. *Iron* - Diuretics do not directly affect iron excretion or absorption. - Iron balance is regulated primarily through intestinal absorption, not renal excretion.

Q: Intravenous furosemide is used for rapid control of symptoms in acute left ventricular failure. It provides quick relief of dyspnoea by :

Causing venodilation. ***Causing venodilation*** - Furosemide, even before significant diuresis, causes rapid **venodilation**, leading to a decrease in **preload** and pulmonary congestion. This reduces the work of the heart and alleviates dyspnoea. - This effect is mediated by the release of **prostaglandins** and is observed within minutes of intravenous administration. *Producing bronchodilation* - Furosemide does not directly cause bronchodilation; it primarily acts on the kidneys and vasculature. - While improved pulmonary edema can secondarily ease breathing, its quick relief of dyspnoea is not due to direct airway relaxation. *Stimulating left ventricular contractility* - Furosemide is a loop diuretic and does not directly enhance **myocardial contractility**; it is not an inotropic agent. - In fact, by reducing preload and afterload, it can indirectly reduce the immediate demand on the failing ventricle. *Causing rapid diuresis and reducing circulating blood volume* - While furosemide does cause rapid diuresis and a reduction in circulating blood volume, these effects typically take longer to fully manifest (around 30 minutes to an hour) when compared to the immediate relief of dyspnoea seen after IV administration. - The initial rapid relief of dyspnoea is attributed more to its vasodilatory properties, reducing cardiac preload.

Q: Gout can be precipitated by -

Thiazide diuretics. ***Thiazide diuretics*** - **Thiazide diuretics** reduce the renal excretion of **uric acid**, leading to increased serum uric acid levels (hyperuricemia). - This elevation in uric acid can lead to the formation of **uric acid crystals** in joints, precipitating a gout attack. *Digitalis* - **Digitalis** (digoxin) is a cardiac glycoside used for heart failure and arrhythmias; it does not directly affect uric acid metabolism. - Its primary mechanism involves inhibiting the **Na+/K+-ATPase pump**, increasing intracellular calcium, and enhancing myocardial contractility. *Calcium channel blockers* - **Calcium channel blockers** primarily act by blocking calcium influx into vascular smooth muscle and cardiac cells. - They are generally considered **neutral** or even slightly beneficial for uric acid levels; some, like amlodipine, have shown potential to lower uric acid slightly. *Omeprazole* - **Omeprazole** is a proton pump inhibitor (PPI) that reduces stomach acid production. - It does not have a direct mechanism that would significantly impact **uric acid metabolism** or precipitate gout.

Question 1

Which of the following is a carbonic anhydrase inhibitor?

Accepted Answer

Acetazolamide

Answer

Hydrochlorothiazide

Answer

Mannitol

Answer

Furosemide

Question 2

Hydrochlorothiazide works by inhibiting

Accepted Answer

Na+ Cl pump in early DCT

Answer

Na+ Cl pump in late DCT

Answer

Na+ K+ 2Cl pump in descending limb of loop of Henle

Answer

Na+ K+ 2Cl pump in ascending limb of loop of Henle

Question 3

Which one of the following is not a clinical use of spironolactone?

Accepted Answer

Pulmonary edema

Answer

Congestive heart failure

Answer

Hypertension

Answer

To counteract hypokalemia due to thiazide diuretics

Question 4

A patient is going skiing high in the Rockies and is given acetazolamide to protect against altitude sickness. Unfortunately, the patient is also a type 1 diabetic. He is admitted to the hospital in a worsening ketoacidosis. In which of the following cells has acetazolamide inhibited a reaction that has led to the severity of the metabolic acidosis?

Accepted Answer

Renal tubular cells

Answer

Cells in the lens of the eye

Answer

Liver cells

Answer

Immune system cells

Question 5

Which of the following diuretics is contraindicated in Hepatic coma?

Accepted Answer

Acetazolamide

Answer

Bumetanide

Answer

Furosemide

Answer

Spironolactone

Question 6

What is the effect of thiazide diuretics on urinary calcium excretion?

Accepted Answer

Decrease excretion

Answer

Increase excretion

Answer

No effect

Answer

Variable effect

Question 7

Side effects of oral carbonic anhydrase inhibitors include?

Accepted Answer

Paresthesia

Answer

Hyperkalemia

Answer

Insomnia

Answer

Weight gain

Question 8

Loop and thiazide diuretics commonly cause clinically significant loss of:

Accepted Answer

Potassium

Answer

Sodium

Answer

Calcium

Answer

Iron

Question 9

Intravenous furosemide is used for rapid control of symptoms in acute left ventricular failure. It provides quick relief of dyspnoea by :

Accepted Answer

Causing venodilation

Answer

Producing bronchodilation

Answer

Stimulating left ventricular contractility

Answer

Causing rapid diuresis and reducing circulating blood volume

Question 10

Gout can be precipitated by -

Accepted Answer

Thiazide diuretics

Answer

Digitalis

Answer

Calcium channel blockers

Answer

Omeprazole

Diuretics — MCQs

Diuretics — MCQs

On this page

Practice by Chapter

Want unlimited practice?