Magnesium Sulfate (OB)
Eclampsia seizure prophylaxis, Eclampsia treatment, Fetal neuroprotection (<32 weeks), Tocolysis (off-label, short-term)
Indications
- Eclampsia seizure prophylaxis
- Eclampsia treatment
- Fetal neuroprotection (<32 weeks)
- Tocolysis (off-label, short-term)
Adult dosing
- preeclampsia prophylaxis: dose: 4; unit: g IV load over 15-20 min, then 1-2 g/hr maintenance; route: IV; fixed: true; eclampsia seizure: dose: 6; unit: g IV load over 15-20 min, then 2 g/hr; route: IV; fixed: true; neuroprotection: dose: 4; unit: g IV load over 20-30 min; route: IV; interval: Then 1g/hr until delivery or 12h; fixed: true
Contraindications
- Myasthenia gravis
- Heart block
Clinical pearls
- Therapeutic range: 4-7 mEq/L
- Toxicity ladder: loss of reflexes (8-12) → respiratory depression (12-15) → cardiac arrest (>15)
- Antidote: calcium gluconate 1g IV over 3 min
- Monitor: patellar reflexes (check q1h), respiratory rate (hold if <12), urine output (hold if <30 mL/hr)
- Continue MgSO4 for 24 hours postpartum
Source and review
- Magpie Trial, Lancet 2002; ACOG Practice Bulletin No. 222. Last reviewed: 2024-11-01