Which of the following is used as an antidote for Organophosphorus poisoning?

WCL Staff Nurse - 2019

Pharmacology

Easy

Appeared in: WCL Staff Nurse - 2019

Explanation

Organophosphorus (OP) compounds cause poisoning by inhibiting the enzyme acetylcholinesterase, leading to an excess of acetylcholine and a subsequent cholinergic crisis.
This crisis manifests with severe muscarinic symptoms like bradycardia, profuse respiratory secretions (bronchorrhea), and bronchospasm, which can be fatal.
Atropine is a competitive antagonist at muscarinic acetylcholine receptors.
By blocking these receptors, atropine directly counteracts the life-threatening muscarinic effects, making it the primary, life-saving antidote in OP poisoning.
It is administered intravenously and titrated until clinical signs of 'atropinization' (dry secretions, increased heart rate, pupil dilation) are observed.

Option B: Adrenaline is a sympathomimetic agent that stimulates alpha and beta-adrenergic receptors. It is not an antidote for OP poisoning as it does not block cholinergic receptors.
Option C: Avil (Pheniramine) is an antihistamine that blocks H1 histamine receptors. It has no effect on the cholinergic system and is therefore ineffective in OP poisoning.
Option D: Amiodarone is a class III antiarrhythmic drug used to manage complex cardiac arrhythmias. It does not have any anticholinergic properties and is not used for OP poisoning.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology: Antidotes for Poisoning as background academic context rather than a clinical decision trigger.
Nurses must be able to rapidly recognize the signs of a cholinergic crisis, often remembered by the mnemonic DUMBBELS: Diarrhea, Urination, Miosis, Bronchospasm/Bronchorrhea, Emesis, Lacrimation, Salivation.
The primary nursing intervention is the prompt administration of IV atropine. The dose is repeated every 5-10 minutes, doubling the dose if needed, until the patient's lungs are clear of secretions and the heart rate is adequate. This is known as achieving 'atropinization'.
What if? If a patient with OP poisoning develops severe muscle weakness and respiratory paralysis despite atropine administration, this indicates significant nicotinic effects. The next step would be to administer Pralidoxime (an oxime), which reactivates the acetylcholinesterase enzyme itself.

How to Approach the Question

First, identify the key concepts in the question stem: 'antidote' and 'Organophosphorus poisoning'.
This is a factual recall question that tests your knowledge of toxicology and emergency pharmacology.
Recall the pathophysiology of OP poisoning: it causes a cholinergic crisis by inhibiting the acetylcholinesterase enzyme, leading to an excess of acetylcholine.
Consider which drug class would counteract the effects of excessive acetylcholine. The main treatment involves blocking the muscarinic receptors.
Evaluate the given options: Atropine is a well-known muscarinic antagonist. Adrenaline, Avil (antihistamine), and Amiodarone (antiarrhythmic) have different mechanisms of action.
Based on this reasoning, select Atropine as the correct antidote for the muscarinic effects of OP poisoning.

Concept Tested & Keywords

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