Diuretics Practice Questions

Q: A 46-year-old male presented to the emergency with muscle weakness and cramping. He has been taking hydrochlorothiazide for recently diagnosed hypertension. Which of the following is the most likely cause of his symptoms?

Hypokalemia. The patient is presenting with classic symptoms of electrolyte imbalance—muscle weakness and cramping—following the initiation of a Thiazide diuretic. **1. Why Hypokalemia is correct:** Thiazide diuretics (like hydrochlorothiazide) act on the distal convoluted tubule (DCT) by inhibiting the Na+/Cl- symporter. This increases the delivery of sodium and water to the collecting duct. In the collecting duct, the increased sodium load promotes sodium reabsorption via ENaC channels, which is coupled with the secretion of potassium (K+) and hydrogen ions (H+) into the urine [1]. This process leads to **Hypokalemia** and metabolic alkalosis. Low serum potassium levels hyperpolarize the muscle cell membrane, leading to muscle weakness, cramps, and in severe cases, paralysis or arrhythmias [1]. **2. Why the other options are incorrect:** * **Hypocalcemia:** Thiazides actually **increase** calcium reabsorption in the DCT (Hypocalciuric effect). Therefore, they are more likely to cause *hypercalcemia*, not hypocalcemia. * **Hyponatremia:** While Thiazides can cause hyponatremia, it typically presents with neurological symptoms (confusion, lethargy, seizures) rather than isolated muscle cramping and weakness. * **Hypoglycemia:** Thiazides are associated with "metabolic side effects" including **hyperglycemia** (due to impaired insulin secretion) and hyperuricemia, not hypoglycemia. **Clinical Pearls for NEET-PG:** * **Thiazide Side Effects (Mnemonic: GLUC):** Hyper**G**lycemia, Hyper**L**ipidemia, Hyper**U**ricemia, Hyper**C**alcemia. * **Electrolyte "Lowers":** Thiazides lower Na+, K+, and Mg2+. * **Drug of Choice:** Thiazides are the preferred diuretics for hypertensive patients with osteoporosis because they decrease urinary calcium excretion, helping to preserve bone density.

Q: What is the drug of choice in lithium-induced diabetes insipidus?

Amiloride. ### Explanation **Correct Option: A. Amiloride** Lithium-induced Nephrogenic Diabetes Insipidus (NDI) occurs because lithium enters the principal cells of the collecting duct through **ENaC (Epithelial Sodium Channels)**. Once inside, lithium inhibits glycogen synthase kinase-3β, interfering with the action of ADH (Vasopressin) and reducing aquaporin-2 expression. **Amiloride** is the drug of choice because it blocks these ENaC channels, preventing lithium from entering the cells and thereby restoring the kidney's concentrating ability. **Why other options are incorrect:** * **B. Vasopressin:** In NDI, the kidneys are resistant to ADH. Therefore, administering exogenous vasopressin will not improve urine concentration. * **C. Thiazide diuretics:** While thiazides are used to treat other forms of NDI (by causing mild volume depletion and increasing proximal water reabsorption), they are not the specific treatment for lithium-induced cases and can actually increase lithium toxicity by decreasing its clearance. * **D. Diclofenac:** NSAIDs can be used in NDI to decrease GFR and inhibit prostaglandins (which antagonize ADH), but they are secondary treatments and carry risks of renal impairment. **High-Yield Clinical Pearls for NEET-PG:** * **Lithium Toxicity:** Thiazides, ACE inhibitors, and NSAIDs (except Aspirin) increase lithium levels and can lead to toxicity. * **Amiloride vs. Triamterene:** Both are K+-sparing diuretics (ENaC blockers), but Amiloride is specifically preferred for lithium-induced NDI. * **DOC for Central DI:** Desmopressin (dDAVP). * **DOC for General NDI:** Thiazides (e.g., Hydrochlorothiazide).

Q: Which of the following metabolic abnormalities is seen with long-term use of spironolactone?

Metabolic acidosis. **Explanation:** Spironolactone is a potassium-sparing diuretic that acts as a competitive antagonist of the mineralocorticoid receptor in the late distal tubule and collecting duct. **Why Metabolic Acidosis is Correct:** Aldosterone normally promotes the reabsorption of sodium ($Na^+$) in exchange for the secretion of potassium ($K^+$) and hydrogen ions ($H^+$) via the $H^+$-ATPase pump in the intercalated cells. By inhibiting aldosterone, spironolactone reduces the secretion of $H^+$ into the tubular lumen. This retention of hydrogen ions in the blood leads to **Hyperchloremic Metabolic Acidosis** (specifically a Normal Anion Gap Metabolic Acidosis). **Analysis of Incorrect Options:** * **B. Metabolic Alkalosis:** This is typically seen with "Loop" and "Thiazide" diuretics. These drugs increase sodium delivery to the distal tubule, stimulating $H^+$ secretion and causing contraction alkalosis. * **C. Hyperkalemia:** While spironolactone **does** cause hyperkalemia (by inhibiting $K^+$ secretion), the question specifically asks for the **metabolic** (acid-base) abnormality. Hyperkalemia is an electrolyte abnormality, not a metabolic one. In the context of acid-base balance, hyperkalemia and metabolic acidosis often coexist. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Spironolactone causes **"High K and Low pH"** (Hyperkalemia and Acidosis). * **Side Effects:** Beyond metabolic changes, it causes **gynecomastia** and impotence in men due to its non-specific anti-androgenic effects (Eplerenone is a more selective alternative). * **Drug of Choice:** It is the DOC for edema in **Cirrhosis** and for treating **Primary Hyperaldosteronism (Conn’s Syndrome)**. * **Mortality Benefit:** It is proven to reduce mortality in patients with Chronic Heart Failure (NYHA Class II-IV).

Q: Spironolactone is most effective for which type of edema?

Cirrhotic edema. **Explanation:** **1. Why Cirrhotic Edema is Correct:** Spironolactone is the **drug of choice** for edema associated with liver cirrhosis. In cirrhosis, there is decreased hepatic clearance of aldosterone and activation of the Renin-Angiotensin-Aldosterone System (RAAS) due to splanchnic vasodilation. This leads to **secondary hyperaldosteronism**, causing significant sodium and water retention. As a competitive antagonist of the Mineralocorticoid Receptor (MR), spironolactone directly counteracts this excess aldosterone, making it more effective here than in other types of edema. **2. Why Other Options are Incorrect:** * **Cardiac Edema:** While spironolactone is used in Heart Failure (HF) to reduce mortality and remodeling (RALES trial), the primary diuretics for acute symptomatic relief of cardiac edema are **Loop diuretics** (e.g., Furosemide) due to their high efficacy and rapid onset. * **Idiopathic Edema:** This is typically managed with weight reduction, salt restriction, or occasionally low-dose thiazides. Spironolactone is not the primary treatment. * **Nutritional Edema:** This is primarily due to hypoproteinemia (low oncotic pressure). Treatment focuses on protein supplementation and addressing the underlying deficiency rather than specific hormonal antagonism. **3. Clinical Pearls for NEET-PG:** * **Mechanism:** Competitive antagonist of aldosterone at the late distal tubule and collecting duct. * **Side Effects:** The most high-yield side effect is **Gynecomastia** (due to non-specific binding to androgen receptors). Eplerenone is a more selective alternative that avoids this. * **Electrolyte Shift:** Always monitor for **Hyperkalemia**, especially if the patient is also on ACE inhibitors. * **Paradoxical Use:** It is also used in **Conn’s Syndrome** (Primary hyperaldosteronism) and Polycystic Ovary Syndrome (PCOS) for its anti-androgenic effects.

Q: Which of the following is NOT caused by thiazide diuretics?

Ototoxicity. Thiazide diuretics (e.g., Hydrochlorothiazide, Chlorthalidone) act on the distal convoluted tubule (DCT) by inhibiting the **Na⁺-Cl⁻ symporter**. **Why Ototoxicity is the Correct Answer:** Ototoxicity is a classic side effect of **Loop diuretics** (like Furosemide and Ethacrynic acid), not Thiazides. Loop diuretics inhibit the Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending limb of Henle; a similar transporter exists in the stria vascularis of the inner ear. Disruption of this transporter leads to electrolyte imbalances in the endolymph, causing tinnitus or hearing loss. Thiazides do not affect this mechanism. **Explanation of Incorrect Options:** * **Hyperuricemia:** Thiazides compete with uric acid for the organic acid secretory pump in the proximal tubule. This leads to decreased uric acid excretion, potentially precipitating gout. * **Hypercalcemia:** Unlike Loop diuretics (which cause hypocalcemia), Thiazides **increase** calcium reabsorption in the DCT. This occurs because the inhibition of Na⁺ entry increases the activity of the Na⁺/Ca²⁺ exchanger on the basolateral membrane. * **Hypokalemia:** By increasing sodium delivery to the late distal tubule and collecting duct, Thiazides stimulate the exchange of Na⁺ for K⁺ (mediated by aldosterone), leading to potassium depletion. **High-Yield NEET-PG Pearls:** * **Mnemonic for Thiazide side effects:** "Hyper **GLUC**" — Hyper**G**lycemia, Hyper**L**ipidemia, Hyper**U**ricemia, Hyper**C**alcemia. * **Clinical Use:** Because they cause hypercalcemia, Thiazides are the diuretic of choice for hypertensive patients with **osteoporosis** or **recurrent calcium oxalate stones** (as they reduce urinary calcium). * **Chlorthalidone** is often preferred over Hydrochlorothiazide due to its longer half-life and superior evidence in reducing cardiovascular events.

Q: Which of the following adverse effects is NOT typically produced by thiazide diuretics?

Hyperkalemia. **Explanation:** Thiazide diuretics (e.g., Hydrochlorothiazide, Chlorthalidone) act on the **Distal Convoluted Tubule (DCT)** by inhibiting the $Na^+/Cl^-$ symporter. The correct answer is **Hyperkalemia** because Thiazides characteristically cause **Hypokalemia**, not hyperkalemia. **1. Why Hyperkalemia is the correct answer (The Mechanism):** Thiazides increase sodium delivery to the late distal tubule and collecting duct. To reabsorb this excess sodium, the body activates the $Na^+/K^+$ exchange mechanism (driven by Aldosterone), leading to increased secretion of Potassium ($K^+$) into the urine. This results in **Hypokalemia**. Hyperkalemia is typically associated with Potassium-sparing diuretics (e.g., Spironolactone) or ACE inhibitors. **2. Analysis of Incorrect Options:** * **Hyperglycemia:** Thiazides inhibit insulin release from the pancreas (due to low $K^+$ levels) and decrease peripheral glucose utilization, leading to elevated blood sugar. * **Hypokalemia:** As explained above, this is a hallmark side effect due to increased $K^+$ excretion in the distal nephron. * **Hyperlipidemia:** Thiazides can cause a transient increase in serum LDL cholesterol and triglycerides. **Clinical Pearls for NEET-PG:** * **The "HYPER" Mnemonic:** Thiazides cause **Hyper**glycemia, **Hyper**lipidemia, **Hyper**uricemia (can precipitate Gout), and **Hyper**calcemia (useful in preventing calcium stones). * **The "HYPO" Mnemonic:** They cause **Hypo**kalemia, **Hypo**magnesemia, and **Hypo**natremia. * **Drug of Choice:** Chlorthalidone is often preferred over Hydrochlorothiazide due to its longer half-life and better evidence in reducing cardiovascular events.

Q: Which diuretic is commonly used in the management of essential hypertension?

Hydrochlorothiazide. **Explanation:** **Hydrochlorothiazide (Option A)** is the correct answer because **Thiazide diuretics** are the first-line diuretic agents for the management of essential hypertension. Their antihypertensive effect occurs in two phases: initially, they reduce blood pressure by decreasing blood volume and cardiac output; long-term, they act as direct vasodilators by reducing intracellular sodium in vascular smooth muscle, which decreases peripheral vascular resistance. **Why other options are incorrect:** * **Amiloride (Option B):** This is a potassium-sparing diuretic. It has weak antihypertensive efficacy when used alone and is primarily used in combination with Thiazides to prevent hypokalemia. * **Furosemide (Option C):** A loop diuretic with a short duration of action (4–6 hours). While potent, it is less effective than Thiazides for essential hypertension unless the patient has concomitant chronic kidney disease (CrCl <30 ml/min) or congestive heart failure. * **Acetazolamide (Option D):** A carbonic anhydrase inhibitor used mainly for glaucoma, altitude sickness, and urinary alkalinization. It is not used for hypertension due to its weak diuretic effect and risk of metabolic acidosis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Chlorthalidone** is often preferred over Hydrochlorothiazide in recent guidelines due to its longer half-life and superior evidence in reducing cardiovascular events. 2. **Metabolic Side Effects of Thiazides:** Remember the "4 Hypers and 2 Hypos": **Hyper**glycemia, **Hyper**lipidemia, **Hyper**uricemia, **Hyper**calcemia; **Hypo**kalemia and **Hypo**natremia. 3. Thiazides are ineffective if the GFR is less than 30 ml/min (except **Metolazone**).

Question 1

Which of the following potassium-sparing diuretics alters cardiac mortality?

Accepted Answer

Spironolactone

Answer

Amiloride

Answer

Triamterene

Answer

Eplerenone

Question 2

A 46-year-old male presented to the emergency with muscle weakness and cramping. He has been taking hydrochlorothiazide for recently diagnosed hypertension. Which of the following is the most likely cause of his symptoms?

Accepted Answer

Hypokalemia

Answer

Hypocalcemia

Answer

Hyponatremia

Answer

Hypoglycemia

Question 3

What is the drug of choice in lithium-induced diabetes insipidus?

Accepted Answer

Amiloride

Answer

Vasopressin

Answer

Thiazide diuretics

Answer

Diclofenac

Question 4

Which of the following metabolic abnormalities is seen with long-term use of spironolactone?

Accepted Answer

Metabolic acidosis

Answer

Metabolic alkalosis

Answer

Hyperkalemia

Answer

None of the above

Question 5

Spironolactone is most useful in?

Accepted Answer

Cirrhotic ascites

Answer

Cardiac hypertrophy

Answer

Exudative pleural effusion

Answer

Renal artery stenosis

Question 6

Spironolactone is most effective for which type of edema?

Accepted Answer

Cirrhotic edema

Answer

Cardiac edema

Answer

Idiopathic edema

Answer

Nutritional edema

Question 7

Which of the following is NOT caused by thiazide diuretics?

Accepted Answer

Ototoxicity

Answer

Hyperuricemia

Answer

Hypercalcemia

Answer

Hypokalemia

Question 8

Which of the following adverse effects is NOT typically produced by thiazide diuretics?

Accepted Answer

Hyperkalemia

Answer

Hyperglycemia

Answer

Hypokalemia

Answer

Hyperlipidemia

Question 9

Which diuretic is commonly used in the management of essential hypertension?

Accepted Answer

Hydrochlorothiazide

Answer

Amiloride

Answer

Furosemide

Answer

Acetazolamide

Question 10

All of the following are true regarding diuretic-associated hypokalemia, EXCEPT:

Accepted Answer

Loop diuretics cause more hypokalemia than thiazide diuretics.

Answer

Increased distal tubular sodium delivery and distal tubular flow rate result in hypokalemia.

Answer

Secondary hyperaldosteronism also plays a role.

Answer

Thiazides cause hypocalciuria.

Diuretics — MCQs

Diuretics — MCQs

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