In a patient on magnesium therapy for preeclampsia, signs of magnesium overdose most commonly include which symptom?

In a patient on magnesium therapy for preeclampsia, signs of magnesium overdose most commonly include which symptom?

• A. Respiratory depression
• B. Hypertension
• C. Seizures
• D. Nausea

Answer: (A)

Magnesium sulfate in preeclampsia works by reducing neuromuscular excitability and CNS activity to prevent seizures. When levels become toxic, the most clinically evident sign is respiratory depression because high magnesium weakens the respiratory muscles and dampens the respiratory drive. Mechanistically, magnesium blocks calcium-dependent neurotransmitter release and depresses neuromuscular transmission, so the diaphragm and other respiratory muscles weaken and breathing slows, which can progress to apnea if not stopped. Hypertension is not typical of magnesium overdose (it tends to cause vasodilation and lower blood pressure), seizures are more associated with insufficient magnesium, and nausea is nonspecific and less predictive of toxicity. In practice, any signs of overdose warrant stopping the infusion and treating emergently, with calcium gluconate as an antidote, while monitoring airway and respiration closely.

Magnesium sulfate in preeclampsia works by reducing neuromuscular excitability and CNS activity to prevent seizures. When levels become toxic, the most clinically evident sign is respiratory depression because high magnesium weakens the respiratory muscles and dampens the respiratory drive. Mechanistically, magnesium blocks calcium-dependent neurotransmitter release and depresses neuromuscular transmission, so the diaphragm and other respiratory muscles weaken and breathing slows, which can progress to apnea if not stopped. Hypertension is not typical of magnesium overdose (it tends to cause vasodilation and lower blood pressure), seizures are more associated with insufficient magnesium, and nausea is nonspecific and less predictive of toxicity. In practice, any signs of overdose warrant stopping the infusion and treating emergently, with calcium gluconate as an antidote, while monitoring airway and respiration closely.