Recognize
- Symptoms: tremor, hyperreflexia, tetany, seizure, weakness
- EKG: prolonged QT, torsades, refractory ventricular arrhythmia
- Causes: GI loss (diarrhea, PPI), diuretics, alcoholism, malnutrition, DKA recovery, refeeding, aminoglycosides, amphotericin
- Often coexists with hypokalemia and hypocalcemia
Torsades / seizure / unstable
- MgSO₄ 2 g IV over 1–2 min for torsades / pulseless
- Eclampsia / severe pre-eclampsia: 4–6 g IV load, then 1–2 g/h
- Severe seizure: 2 g IV over 10 min
Symptomatic IV
- MgSO₄ 1–2 g IV over 30–60 min · repeat to total 4–8 g/24 h PRN
- Slow infusion to avoid flushing, hypotension, nausea
- Check Mg q12h · ~50% of dose excreted in urine
Mild / asymptomatic
- Mg oxide 400–800 mg PO daily (diarrhea limits dose)
- Address underlying cause (PPI, diuretic, alcohol)
Caution
- Renal failure: reduce dose 50% — risk of hypermagnesemia
- Always recheck K and Ca after Mg corrected