An antidote for the toxicity of magnesium sulphate is

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2022

Explanation

Calcium gluconate is the specific antidote for magnesium sulfate toxicity.
It acts as a direct physiological antagonist, competing with magnesium ions at the neuromuscular junction and on cardiac muscle.
This action rapidly reverses the most dangerous effects of hypermagnesemia, which include respiratory depression, loss of deep tendon reflexes, and cardiac arrest.
Administering intravenous calcium directly counteracts the neuromuscular and cardiac effects of excess extracellular magnesium.

Option A: Acetylcysteine is not used for magnesium toxicity. Its mechanism is specific to replenishing glutathione for paracetamol (acetaminophen) detoxification.
Option B: Protamine sulphate has no effect on magnesium levels or toxicity. It is a basic protein that binds specifically to heparin.
Option C: Naloxone is an opioid receptor antagonist and does not affect the neuromuscular blockade caused by magnesium.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology: Antidotes for Drug Toxicity as background academic context rather than a clinical decision trigger.
Recognizing the signs of magnesium toxicity is a critical nursing responsibility, especially in obstetric patients receiving it for pre-eclampsia. The first sign is often the loss of deep tendon reflexes (e.g., patellar reflex).
Nurses must always have the antidote, calcium gluconate, readily available at the bedside whenever a patient is on a magnesium sulfate infusion.
Patient safety depends on frequent monitoring of respiratory rate, oxygen saturation, level of consciousness, and urine output, as deterioration can be rapid.

How to Approach the Question

This is a factual recall question that tests your knowledge of common pharmacological antidotes.
First, identify the key drug in the question: 'magnesium sulphate'.
Next, identify the core question: what is the 'antidote' for its 'toxicity'?
Systematically review the options, recalling the specific use for each antidote.
Recall that Acetylcysteine is for paracetamol, Protamine sulphate is for heparin, and Naloxone is for opioids.
By elimination and direct recall, identify Calcium gluconate as the specific antagonist for magnesium sulfate.

Concept Tested & Keywords

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E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 67-69

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 752-754

Practise the full RUHS, Jaipur, M.Sc Nursing Entrance Exam-2022

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