Which of the following medications can worsen anaphylactic shock by blocking the effects of epinephrine?

RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Pharmacology

Medium

Appeared in: RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Explanation

Beta-blockers occupy the same beta-adrenergic receptors that epinephrine needs to stimulate to reverse the effects of anaphylaxis.
This pharmacological antagonism makes standard doses of epinephrine less effective or completely ineffective, leading to a dangerous condition called refractory anaphylaxis.
Non-selective beta-blockers are particularly problematic as they block both beta-1 (heart) and beta-2 (lung) receptors, directly opposing epinephrine's action on bronchodilation and cardiac output.
The result is persistent hypotension and bronchospasm despite epinephrine administration, requiring alternative treatments like glucagon.

Option A: ACE inhibitors do not block epinephrine receptors. Their association with anaphylaxis is due to increasing bradykinin levels, which can cause angioedema, but they don't prevent epinephrine from working.
Option B: Corticosteroids are a second-line treatment for anaphylaxis. They work slowly to reduce inflammation and prevent a delayed reaction; they do not block epinephrine's immediate effects.
Option C: Antihistamines are an adjunctive treatment that blocks histamine receptors to relieve symptoms like itching and hives. They do not affect the adrenergic receptors targeted by epinephrine.

Visual 1: Diagram - A diagram illustrating a beta-adrenergic receptor. One panel shows epinephrine binding and causing a cellular response (e.g., bronchodilation). The second panel shows a beta-blocker molecule physically blocking the receptor, preventing epinephrine from binding.
Visual 2: Flowchart - A clinical algorithm for managing anaphylaxis, with a specific branch for 'Refractory Anaphylaxis in a Patient on Beta-Blockers,' showing the steps: repeat epinephrine, consider IV epinephrine, and administer glucagon.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacological antagonism and its impact on the management of anaphylaxis as background academic context rather than a clinical decision trigger.
This highlights the critical importance of obtaining a thorough medication history for every patient, especially those with known severe allergies. Knowing a patient is on a beta-blocker changes the emergency management plan for anaphylaxis.
Nurses must be prepared for refractory anaphylaxis in patients taking beta-blockers. This includes knowing the rationale for and anticipating the need to administer glucagon, which acts via a different pathway to increase heart rate and contractility.
What if? If the patient was taking a calcium channel blocker instead of a beta-blocker, it would not directly block epinephrine's effects. However, it could contribute to hypotension, potentially complicating management, but the primary antagonism seen with beta-blockers would not occur.

How to Approach the Question

First, identify the core of the question: which drug interferes with the action of epinephrine during anaphylaxis?
Recall the mechanism of action of epinephrine in anaphylaxis: it stimulates alpha and beta-adrenergic receptors to counteract vasodilation, bronchoconstriction, and hypotension.
Analyze each option based on its pharmacological class and mechanism of action.
Consider how each drug class interacts with the adrenergic system. A 'blocker' is a key term that suggests antagonism.
Evaluate 'Beta-blockers'. By definition, they block beta-receptors, the direct targets of epinephrine for bronchodilation and cardiac effects. This makes them the most likely answer.
Rule out the other options by confirming their mechanisms do not involve direct antagonism of epinephrine's primary life-saving actions (e.g., antihistamines block histamine receptors, corticosteroids are anti-inflammatory).

Concept Tested & Keywords

Concept Tested: Pharmacological antagonism and its impact on the management of anaphylaxis.
Stem keywords: medications, worsen anaphylactic shock, blocking effects, epinephrine
Lead-in keywords: Which

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