A woman with eclampsia develops generalised tonic-clonic convulsions despite IV magnesium sulfate (loading dose given). Serum magnesium is 6 mEq/L. What is the MOST appropriate next step?
- A Administer IV diazepam 10 mg as seizure rescue
- B Switch to phenytoin 15 mg/kg IV loading dose
- C Give an additional 2 g magnesium sulfate IV over 20 minutes ✓
- D Perform urgent CT head to rule out intracranial hemorrhage
Correct answer: C. Give an additional 2 g magnesium sulfate IV over 20 minutes
Explanation
When a breakthrough seizure occurs on magnesium therapy with a subtherapeutic or low-normal level (therapeutic range 4–7 mEq/L), the recommended action is an additional bolus of 2 g magnesium sulfate IV over 15–20 minutes. At level 6 mEq/L, further magnesium is safe and should be tried first. CT head is appropriate if focal neurology or persistent coma suggests intracranial pathology, but is not the immediate first step for breakthrough seizure. Phenytoin and diazepam are second-line agents not routinely used in eclampsia management.
Reference: Williams Obstetrics, 26th ed.
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