What is the antidote for magnesium sulfate toxicity?

• A. Naloxone
• B. Calcium chloride
• C. Potassium chloride
• D. Calcium gluconate

Answer: (D)

When magnesium sulfate accumulates to toxic levels, it depresses neuromuscular transmission and heart conduction. The antidote is IV calcium gluconate, which provides calcium ions that oppose magnesium’s effects. Giving calcium gluconate rapidly reverses the impaired neuromuscular function and helps stabilize the heart, reversing symptoms like reduced reflexes and respiratory or cardiovascular depression. Calcium gluconate is preferred because it is effective and safer to administer IV than some other calcium salts. Naloxone would address opioid overdose, not magnesium toxicity; potassium chloride has no role as an antidote for magnesium toxicity; calcium chloride can counteract magnesium but is less favored due to higher risk of tissue irritation and other concerns.