Loop diuretics – Furosemide MCQs With Answer

Loop diuretics, especially furosemide, are cornerstone drugs in clinical pharmacology taught in B. Pharm. This topic covers mechanism of action, pharmacokinetics, therapeutic uses, adverse effects, drug interactions, and monitoring parameters. Key concepts include inhibition of the Na+-K+-2Cl- cotransporter in the thick ascending limb, rapid onset with intravenous use, renal secretion via organic acid transporters, and risks like hypokalemia, ototoxicity, and metabolic alkalosis. Understanding potency differences (bumetanide, torsemide), effects on calcium handling, and clinical indications such as pulmonary edema and hypercalcemia is essential for safe patient care and rational prescribing. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which transporter is the primary molecular target of furosemide in the nephron?

• Inhibition of Na+-Cl- cotransporter in distal convoluted tubule
• Inhibition of Na+-K+-2Cl- cotransporter in thick ascending limb
• Inhibition of epithelial sodium channel (ENaC) in collecting duct
• Inhibition of sodium-hydrogen exchanger in proximal tubule

Correct Answer: Inhibition of Na+-K+-2Cl- cotransporter in thick ascending limb

Q2. Furosemide primarily increases urinary excretion of which electrolyte?

• Magnesium more than sodium
• Calcium while conserving sodium
• Sodium, potassium, and chloride
• Pottasium-sparing effect with increased bicarbonate

Correct Answer: Sodium, potassium, and chloride

Q3. The major route by which furosemide reaches its luminal site of action is:

• Glomerular filtration only
• Passive diffusion across luminal membrane
• Secretion into proximal tubule via organic anion transporters
• Active uptake by distal tubule cells from blood

Correct Answer: Secretion into proximal tubule via organic anion transporters

Q4. A common serious adverse effect associated with high-dose intravenous furosemide is:

• Gastrointestinal bleeding
• Ototoxicity (hearing loss or tinnitus)
• Severe hypercalcemia
• Bradycardia due to vagal stimulation

Correct Answer: Ototoxicity (hearing loss or tinnitus)

Q5. Furosemide causes metabolic alkalosis primarily because of:

• Direct stimulation of bicarbonate reabsorption in proximal tubule
• Volume contraction leading to increased aldosterone and H+ secretion
• Direct inhibition of carbonic anhydrase in the collecting duct
• Increased renal production of ammonia

Correct Answer: Volume contraction leading to increased aldosterone and H+ secretion

Q6. Which clinical indication is MOST appropriate for intravenous furosemide?

• Chronic hypertension controlled with thiazides
• Acute pulmonary edema with severe dyspnea
• Prophylaxis of migraine headaches
• Management of uncomplicated urinary tract infection

Correct Answer: Acute pulmonary edema with severe dyspnea

Q7. Co-administration of furosemide with NSAIDs often results in:

• Enhanced diuretic effect due to increased prostaglandins
• Reduced diuretic effect due to inhibition of renal prostaglandin synthesis
• No interaction because NSAIDs act on the liver
• Protection against ototoxicity

Correct Answer: Reduced diuretic effect due to inhibition of renal prostaglandin synthesis

Q8. Which laboratory change is typically seen after loop diuretic therapy?

• Hypokalemia and hypomagnesemia
• Hyperkalemia and hypermagnesemia
• Hypouricemia and hyponatremia without potassium change
• Decreased blood urea nitrogen (BUN) only

Correct Answer: Hypokalemia and hypomagnesemia

Q9. Regarding calcium handling, loop diuretics typically:

• Decrease urinary calcium excretion
• Increase urinary calcium excretion
• Have no effect on calcium excretion
• Cause sustained hypocalcemia by bone resorption

Correct Answer: Increase urinary calcium excretion

Q10. Which statement about oral bioavailability of furosemide is correct?

• Furosemide has consistent 100% oral bioavailability
• Bioavailability is variable and can be reduced in heart failure or gut edema
• Furosemide is not absorbed orally and must be given IV
• Bioavailability is increased when taken with antacids

Correct Answer: Bioavailability is variable and can be reduced in heart failure or gut edema

Q11. Which diuretic is more potent (per mg) than furosemide?

• Hydrochlorothiazide
• Bumetanide
• Spironolactone
• Chlorthalidone

Correct Answer: Bumetanide

Q12. Furosemide-induced hypokalemia can be minimized clinically by co-prescribing:

• An ACE inhibitor or angiotensin receptor blocker (may worsen hyperkalemia)
• A potassium-sparing diuretic such as spironolactone or amiloride
• A loop diuretic at higher dose
• Oral calcium supplements

Correct Answer: A potassium-sparing diuretic such as spironolactone or amiloride

Q13. The mechanism by which furosemide can precipitate gout is:

• Increased renal uric acid excretion causing hypouricemia
• Reduced urate secretion in proximal tubule leading to hyperuricemia
• Direct stimulation of xanthine oxidase increasing uric acid production
• Enhanced dietary purine absorption

Correct Answer: Reduced urate secretion in proximal tubule leading to hyperuricemia

Q14. In heart failure patients, loop diuretics improve symptoms mainly by:

• Increasing cardiac contractility directly
• Reducing preload and pulmonary congestion via diuresis
• Causing peripheral vasodilation via nitric oxide release
• Blocking beta-adrenergic receptors

Correct Answer: Reducing preload and pulmonary congestion via diuresis

Q15. Which is TRUE about furosemide dosing and onset?

• Oral furosemide acts within 5–10 minutes
• IV furosemide has a faster onset than oral and a large peak effect
• Furosemide has delayed onset when given IV compared to oral
• Furosemide duration is longer after IV than oral

Correct Answer: IV furosemide has a faster onset than oral and a large peak effect

Q16. Which of the following drug interactions increases risk of ototoxicity with furosemide?

• Concurrent use of aminoglycoside antibiotics
• Concomitant NSAID use
• Co-administration with ACE inhibitors
• Use with potassium supplements

Correct Answer: Concurrent use of aminoglycoside antibiotics

Q17. A pharmacodynamic difference between thiazides and loop diuretics is that loops:

• Require adequate renal function to be effective and are weak when GFR is low
• Are more effective than thiazides in patients with reduced renal function (low GFR)
• Primarily increase calcium reabsorption like thiazides
• Act mainly on the collecting duct

Correct Answer: Are more effective than thiazides in patients with reduced renal function (low GFR)

Q18. Which monitoring parameter is most important during high-dose loop diuretic therapy?

• Serial chest X-rays
• Electrolytes including potassium and magnesium
• Serum amylase levels
• Thyroid function tests

Correct Answer: Electrolytes including potassium and magnesium

Q19. Which statement about furosemide and pregnancy is correct?

• Furosemide is absolutely contraindicated in pregnancy due to teratogenicity
• Furosemide can be used in pregnancy when benefits outweigh risks but monitoring is needed
• Furosemide is a first-line diuretic for gestational hypertension
• Furosemide causes irreversible fetal renal agenesis

Correct Answer: Furosemide can be used in pregnancy when benefits outweigh risks but monitoring is needed

Q20. The “ceiling effect” of loop diuretics refers to:

• A maximal diuretic response beyond which higher doses produce no further natriuresis
• Progressive tachyphylaxis where even low doses lose effect rapidly
• A limit to oral absorption causing adverse GI effects
• An upper limit of potassium retention despite increasing dose

Correct Answer: A maximal diuretic response beyond which higher doses produce no further natriuresis

Q21. Which structural/chemical property influences furosemide’s renal secretion?

• High lipophilicity allowing passive diffusion into lumen
• Negatively charged organic acid moiety facilitating secretion via OATs
• Basic amine group that binds to distal tubule receptors
• Peptide backbone requiring proteolytic activation

Correct Answer: Negatively charged organic acid moiety facilitating secretion via OATs

Q22. In a patient with hypercalcemia, the diuretic of choice to enhance calcium excretion is:

• Hydrochlorothiazide
• Furosemide (after adequate hydration)
• Spironolactone
• Amiloride

Correct Answer: Furosemide (after adequate hydration)

Q23. Which adverse effect is specifically associated with excess diuresis from loop diuretics?

• Hypervolemia leading to hypertension
• Dehydration and hypotension with prerenal azotemia
• Elevated intracranial pressure
• Excessive weight gain

Correct Answer: Dehydration and hypotension with prerenal azotemia

Q24. Torsemide differs from furosemide in that torsemide:

• Has shorter half-life and less oral bioavailability than furosemide
• Has longer half-life and more predictable oral bioavailability than furosemide
• Is a thiazide-class diuretic, not a loop diuretic
• Causes hypocalcemia less frequently than furosemide

Correct Answer: Has longer half-life and more predictable oral bioavailability than furosemide

Q25. Which is TRUE about combined use of loop diuretics and thiazides?

• They have antagonistic effects and should never be combined
• Sequential nephron blockade may produce profound diuresis and hypokalemia
• Combination eliminates risk of volume depletion
• Thiazides prevent loop-induced ototoxicity

Correct Answer: Sequential nephron blockade may produce profound diuresis and hypokalemia

Q26. Resistance to loop diuretics in chronic heart failure can be due to:

• Decreased renal organic anion secretion and increased distal sodium reabsorption
• Excessive use of potassium supplements only
• Primary hepatic metabolism increasing active drug levels
• Enhanced luminal binding resulting in increased effect

Correct Answer: Decreased renal organic anion secretion and increased distal sodium reabsorption

Q27. Which ECG change might be expected with significant furosemide-induced hypokalemia?

• Peaked T waves typical of hyperkalemia
• U waves and flattened T waves
• Prolonged PR interval only
• No ECG changes occur with hypokalemia

Correct Answer: U waves and flattened T waves

Q28. The effect of loop diuretics on the kidney’s countercurrent multiplier includes:

• Enhancement of medullary hypertonicity and urine concentration
• Disruption of countercurrent multiplier reducing urine concentrating ability
• No effect on renal concentrating mechanism
• Direct increase in ADH release causing concentrated urine

Correct Answer: Disruption of countercurrent multiplier reducing urine concentrating ability

Q29. Which statement best describes furosemide’s elimination?

• Primarily hepatic metabolism to inactive metabolites
• Mainly renal excretion after tubular secretion with partial hepatic metabolism
• Cleared exclusively by bile and feces
• Eliminated unchanged through sweat glands

Correct Answer: Mainly renal excretion after tubular secretion with partial hepatic metabolism

Q30. Which precaution is most important before giving an intravenous bolus of high-dose furosemide?

• Confirm absence of sulfonamide allergy has no relevance
• Assess current blood pressure, volume status, and serum electrolytes
• Ensure patient has recent echocardiogram only
• Administer concurrently with IV aminoglycoside to enhance effect

Correct Answer: Assess current blood pressure, volume status, and serum electrolytes

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