A woman receiving magnesium sulfate for eclampsia prophylaxis develops respiratory depression and the knee jerks are absent. Which immediate action is correct?

• A Give frusemide 40 mg intravenously to accelerate renal excretion
• B Give naloxone 0.4 mg intravenously and continue the infusion at half rate
• C Stop the infusion and give calcium gluconate 10% 10 mL intravenously ✓
• D Intubate immediately before any drug is administered

Explanation

Magnesium sulfate toxicity progresses in a predictable order: loss of patellar reflexes around 7 mEq/L, then respiratory depression around 10 mEq/L, then cardiac arrest. Management is to stop the infusion and give calcium gluconate 10%, 10 mL intravenously slowly as the specific antagonist. Naloxone reverses opioids, not magnesium. Intubation may be needed but the antidote comes first.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.