Magnesium Sulfate Administration in Obstetrics

Standard Dosing Protocol

The American College of Obstetricians and Gynecologists recommends administering magnesium sulfate as a 4-6 gram IV loading dose over 20-30 minutes, followed by a continuous maintenance infusion of 2 grams per hour, particularly in patients with BMI ≥25 kg/m² 1
This achieves rapid therapeutic levels for seizure prevention in severe preeclampsia 1

Magnesium sulfate is the most effective agent for preventing eclamptic seizures, superior to phenytoin and diazepam, as recommended by the American College of Obstetricians and Gynecologists 1, 2
The American Heart Association indicates that magnesium sulfate is indicated for severe preeclampsia with blood pressure ≥160/110 mmHg with significant proteinuria, or moderate hypertension with proteinuria and neurological symptoms (headache, visual disturbances, clonus) 1, 3
Approximately halves the seizure rate in patients with preeclampsia, according to the American College of Obstetricians and Gynecologists 3
The American Academy of Pediatrics recommends administering magnesium sulfate when delivery is anticipated before 32 weeks gestation 4, 5
Reduces cerebral palsy risk (relative risk 0.68, 95% CI 0.54-0.87) without increasing mortality, as stated by the American College of Obstetricians and Gynecologists 2

The American College of Obstetricians and Gynecologists recommends continuing magnesium sulfate for 24 hours postpartum in most cases 3
Some evidence suggests that if a woman has received at least 8 grams before delivery, continuing for a further 24 hours postpartum may not provide additional benefit, according to the American College of Obstetricians and Gynecologists 3

Check patellar reflexes before each dose—loss of reflexes indicates impending toxicity at 3.5-5 mmol/L, as recommended by the American College of Obstetricians and Gynecologists 1
Maintain respiratory rate >12 breaths per minute (respiratory paralysis occurs at 5-6.5 mmol/L), according to the American Thoracic Society 1
Ensure urine output ≥30 mL/hour, as magnesium is renally excreted and oliguria increases toxicity risk, as stated by the American College of Obstetricians and Gynecologists 3, 2
Maintain oxygen saturation >90%, as recommended by the American College of Obstetricians and Gynecologists 1, 3

Do not use magnesium sulfate with calcium channel blockers (especially nifedipine), as this causes severe myocardial depression and precipitous hypotension, according to the American Heart Association 3, 2
Limit total fluid intake to 60-80 mL/hour to prevent pulmonary edema, as recommended by the American College of Obstetricians and Gynecologists 1, 3

Aim for euvolemia—avoid "running dry" as preeclamptic patients are at risk for acute kidney injury, but also avoid fluid overload, according to the American College of Obstetricians and Gynecologists 3