Indication
Eclampsia, severe pre-eclampsia, torsades, severe asthma, AF in critically ill.
Preparation
Pre-mix 50% (5 g in 10 mL) diluted further depending on use.
Dilution
Loading: 4 g in 100 mL NS over 15 min. Maintenance: 5 g in 50 mL NS at 1 g/h.
Rate
Eclampsia: 4 g loading over 5–10 min then 1 g/h × 24 h. Torsades: 2 g IV over 10 min.
Monitoring
- • Patellar reflexes (loss = toxicity)
- • RR ≥12, urine output ≥30 mL/h
- • Mg level (target 2–3.5 mmol/L for eclampsia)
Common errors
- • Mg toxicity: calcium gluconate 10 mL 10% IV antidote
- • Maintenance without first checking reflexes
Pearls
- • Reduces recurrent eclampsia by 50% vs phenytoin/diazepam (Magpie trial)
