Magnesium Sulfate Therapy for Preeclampsia

Clinical Indications and Efficacy

The American College of Cardiology recommends magnesium sulfate as an effective treatment for preventing eclampsia, approximately halving the seizure rate in patients with preeclampsia 1, 2, 3
The American Heart Association suggests that all women with preeclampsia in low and middle-income countries should receive magnesium sulfate due to its favorable cost-benefit ratio 1
In high-income settings, the European Society of Cardiology recommends selective use of magnesium sulfate for women with severe hypertension (≥160/110 mmHg) with significant proteinuria (≥3+), or moderate hypertension (≥150/100 mmHg) with at least 2+ proteinuria and signs/symptoms of imminent eclampsia (headache, visual disturbances, clonus) 1, 3, 4

The American College of Obstetricians and Gynecologists recommends continuing magnesium sulfate for 24 hours postpartum in most cases 1, 4
Some evidence suggests that if a woman has received at least 8 g of magnesium sulfate before delivery, continuing for a further 24 hours postpartum may not provide additional benefit, as stated by the National Institute of Child Health and Human Development 1

The American Association for the Study of Liver Diseases recommends magnesium sulfate for women with HELLP syndrome to prevent eclamptic seizures 5, 6
The Society for Maternal-Fetal Medicine suggests using magnesium sulfate as a neuroprotective agent for preterm preeclampsia if delivery is required before 32 weeks' gestation 5
The European Society of Cardiology recommends fluid balance to aim for euvolemia with total fluid intake limited to 60-80 mL/hour to avoid risks of pulmonary edema 1

The European Heart Journal warns against using calcium channel blockers (especially nifedipine) with magnesium sulfate without careful monitoring, as this combination may cause precipitous blood pressure drop 7
The American College of Cardiology advises against "running dry" a preeclamptic woman, as she is already at risk of acute kidney injury, and recommends maintaining adequate hydration while avoiding fluid overload 1
The American Heart Association suggests that reduced gastrointestinal motility during labor may decrease absorption of oral medications, so IV administration may be needed for reliable effect 1

Preeclampsia may worsen or appear de novo after delivery, particularly between days 3-6 postpartum, as acknowledged by six guidelines from the American College of Obstetricians and Gynecologists 8, 9, 10

Continuous maternal administration of magnesium sulfate beyond 5-7 days can cause fetal abnormalities and is contraindicated, with a maximum dosage of 20 grams/48 hours in severe renal insufficiency, and serum magnesium levels of 6 mg/100 mL considered optimal for seizure control 8, 9, 10