Long-term use of furosemide (Lasix) causes which of the following side effects?

NORCET 1 - 2020

Pharmacology

Easy

Appeared in: NORCET 1 - 2020

Explanation

Furosemide is a loop diuretic that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle.
This inhibition prevents the reabsorption of sodium, leading to increased sodium excretion in the urine (natriuresis).
Prolonged and significant sodium loss through the urine directly causes hyponatremia (low blood sodium levels).
Hyponatremia is a common and clinically significant adverse effect of long-term furosemide therapy.

Option A: Furosemide causes potassium wasting by increasing its excretion in the urine. This leads to hypokalemia (low potassium), the opposite of hyperkalemia.
Option C: While furosemide does cause the excretion of dilute urine, leading to a decreased urine specific gravity, hyponatremia is a more direct, specific, and clinically critical electrolyte imbalance resulting from its long-term use.
Option D: Furosemide increases the excretion of hydrogen and chloride ions, leading to a state of hypochloremic metabolic alkalosis (an increase in blood pH).

Visual 1: Diagram: A diagram of the nephron highlighting the thick ascending limb of the loop of Henle, showing the site of action for furosemide and the Na-K-2Cl cotransporter.
Visual 2: Flowchart: A flowchart illustrating how furosemide administration leads to electrolyte imbalances, starting from Na-K-2Cl inhibition and branching to hyponatremia, hypokalemia, and metabolic alkalosis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacological side effects of loop diuretics as background academic context rather than a clinical decision trigger.
Nurses must meticulously monitor serum electrolytes, especially sodium and potassium, in patients receiving long-term furosemide therapy to prevent life-threatening complications like cardiac arrhythmias (from hypokalemia) or neurological changes (from hyponatremia).
Patient education is a critical nursing role. Teaching patients to recognize symptoms of electrolyte imbalance (e.g., muscle weakness, cramps, confusion, dizziness) and the importance of dietary potassium intake is essential for safety.
What if the patient also has renal failure? The risk of electrolyte disturbances and dehydration is significantly higher. The dose of furosemide may need to be adjusted, and monitoring becomes even more critical. In severe renal failure, loop diuretics may become less effective.

How to Approach the Question

First, identify the drug mentioned: Furosemide (Lasix). Classify it as a loop diuretic.
Recall the primary mechanism of action for loop diuretics: inhibition of the Na-K-2Cl cotransporter in the loop of Henle.
Think through the consequences of this inhibition. Blocking reabsorption of Na+, K+, and Cl- means these electrolytes will be lost in the urine.
Evaluate each option based on this mechanism: A) Loss of K+ causes hypo-, not hyperkalemia. B) Loss of Na+ causes hyponatremia. C) Increased water and solute excretion affects urine specific gravity. D) Loss of H+ and Cl- causes metabolic alkalosis, not acidosis.
Compare the correct effects. Both hyponatremia and decreased urine specific gravity are effects, but hyponatremia is a major, clinically monitored side effect, making it the best answer.

Concept Tested & Keywords

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