Assertion (A): Patients with decreased potassium have an increased risk of digoxin toxicity.Reason (R): Because digoxin binds to the Na+/K+-ATPase pump's Na+ site.Choose the correct answer:

Appeared in: BHU NO - 12 April 2024

Explanation

Assertion (A) is correct. Low serum potassium (hypokalemia) is a well-established risk factor that increases the likelihood of digoxin toxicity.
Reason (R) is incorrect. Digoxin exerts its effect by binding to the potassium (K+) binding site of the Na+/K+-ATPase enzyme, not the sodium (Na+) site.
The mechanism involves competition between digoxin and potassium ions for these binding sites. When potassium levels are low, there is less competition, allowing more digoxin to bind to the pump.
This increased binding enhances the inhibitory effect of digoxin on the pump, leading to an increased intracellular calcium concentration and a greater risk of toxicity, including arrhythmias.
Since the Reason (R) provides a factually incorrect statement about the binding site, it cannot be the correct explanation for the Assertion (A).

Option A: This option states that both (A) and (R) are correct. However, Reason (R) is factually incorrect as digoxin binds to the K+ site, not the Na+ site.
Option B: This option claims both statements are correct and that (R) explains (A). This is incorrect because Reason (R) is a factually false statement.
Option C: This option incorrectly states that Assertion (A) is not correct. The link between hypokalemia and increased risk of digoxin toxicity is a critical and well-documented clinical fact.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The relationship between digoxin toxicity, its mechanism of action, and serum potassium levels as background academic context rather than a clinical decision trigger.
Nurses must diligently monitor serum potassium levels in patients receiving digoxin. The normal range is 3.5-5.0 mEq/L. Levels below 3.5 mEq/L warrant notifying the healthcare provider.
Patients on digoxin are often also prescribed diuretics (like furosemide) for heart failure, which can deplete potassium, further increasing the risk of toxicity. This drug combination requires vigilant electrolyte monitoring.
Early signs of digoxin toxicity include anorexia, nausea, vomiting, visual disturbances (yellow-green halos), confusion, and cardiac arrhythmias (like bradycardia or heart block).

How to Approach the Question

First, analyze Assertion (A) for its factual accuracy. Recall or look up the relationship between potassium levels and digoxin toxicity. You should identify that low potassium increases the risk.
Second, analyze Reason (R) for its factual accuracy. Focus on the specific details of digoxin's mechanism of action. The key here is the binding site on the Na+/K+-ATPase pump.
Determine if digoxin binds to the sodium (Na+) or potassium (K+) site. Your knowledge should point to competition with potassium, meaning it binds to the K+ site. This makes Reason (R) incorrect.
Based on your analysis, (A) is correct and (R) is incorrect.
Select the option that matches this conclusion: '(A) is correct, but (R) is not correct'.

Concept Tested & Keywords

Concept Tested: The relationship between digoxin toxicity, its mechanism of action, and serum potassium levels.
Stem keywords: digoxin toxicity, decreased potassium, hypokalemia, Na+/K+-ATPase pump
Lead-in keywords: Assertion (A), Reason (R)

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Practise the full BHU NO - 12 April 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.