Which of the following drugs is commonly administered for a patient with supraventricular tachycardia which also has a short half-life?

1. A

   Metoprolol

2. B

   Adenosine

3. C

   Captopril

4. D

   Amiodarone

Appeared in: RML MAINS 2025

Explanation

• Adenosine is the first-line drug of choice for the prompt conversion of paroxysmal supraventricular tachycardia (SVT) to sinus rhythm.
• It works by activating potassium currents in the atrioventricular (AV) node, which causes hyperpolarization, slows conduction, and interrupts the re-entry pathway of the tachycardia.
• Its defining characteristic is an extremely short half-life of less than 10 seconds, which requires it to be given as a rapid IV bolus followed by a saline flush to ensure it reaches the heart.
• A brief period of asystole or bradycardia is a common and expected effect after administration.

Why Other Options Were Wrong

• Option A: Metoprolol is a beta-blocker with a half-life of 3-7 hours. While it can be used for rate control in SVT, it is not a short-acting agent for acute termination.
• Option C: Captopril is an ACE inhibitor used for hypertension and heart failure. It has no direct antiarrhythmic properties for treating SVT.
• Option D: Amiodarone has an exceptionally long half-life, ranging from 25 to 110 days. This makes it unsuitable for a situation requiring a drug with a short half-life for rapid termination.

Related Visual

Clinical Relevance

• Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Pharmacological management of supraventricular tachycardia (SVT) and drug half-life in acute care settings.
• Administering adenosine requires specific techniques (rapid push, immediate flush) and close monitoring due to the expected brief period of asystole, which can be alarming for both the nurse and the patient.
• Patient education is crucial to prepare them for the transient, uncomfortable side effects like chest pressure, flushing, and a sense of impending doom, which helps reduce anxiety.
• What if? If the patient with SVT were hemodynamically unstable (e.g., hypotensive, altered mental status), the correct immediate action would be synchronized cardioversion, not adenosine.

How to Approach the Question

• First, identify the two key requirements from the question stem: the drug must treat supraventricular tachycardia (SVT) and have a short half-life.
• The term 'short half-life' implies the drug is used for acute, rapid termination of the arrhythmia, not for long-term maintenance.
• Evaluate each option against these two criteria.
• Recall or look up the properties of Adenosine. It is the classic drug for terminating stable SVT and is well-known for its ultra-short half-life (less than 10 seconds).
• Consider the other options. Metoprolol is a beta-blocker with a longer half-life. Captopril is an ACE inhibitor and not an antiarrhythmic. Amiodarone is a potent antiarrhythmic but has a very long half-life.
• Conclude that Adenosine is the only option that fits both criteria perfectly.

Concept Tested & Keywords

• Concept Tested: Pharmacological management of supraventricular tachycardia (SVT) and drug half-life.
• Stem keywords: supraventricular tachycardia, short half-life, drug
• Lead-in keywords: Which
• Clinical cues: Supraventricular tachycardia indicates an arrhythmia originating above the ventricles.
• Clinical cues: Short half-life points to a drug for acute termination, not long-term control.

Question ID

Qt91iurcQtKzJf2J4nMUQB

Copy ID

Reference Book

E6 Pharmacology Katzung 16e p. 379-381

E6 Medicine Davidson Principles Practice 24e p. 502-504

E6 Obstetrics Williams p. 53-73