How do you treat magnesium deficiency in a hospitalized patient?

Treatment of Magnesium Deficiency in Hospitalized Patients

For hospitalized patients with magnesium deficiency, IV magnesium sulfate 2 grams administered over 20 minutes is the recommended initial treatment for mild to moderate hypomagnesemia, with a target serum level >1.5 mg/dL. 1

Assessment and Diagnosis

• Normal plasma magnesium levels range from 1.5-2.5 mEq/L (1.8-3.0 mg/dL)
• Deficiency is defined as levels <1.3 mEq/L (<1.5 mg/dL) 1
• Check serum magnesium levels in patients:
  • With muscle cramps
  • On diuretic therapy
  • With liver disease
  • At risk for QT prolongation
  • With cardiac arrhythmias

Treatment Protocol for Hospitalized Patients

Mild to Moderate Hypomagnesemia:

1. Initial Treatment:

   • IV magnesium sulfate 2 grams over 20 minutes 1, 2
   • Dilute to concentration of 20% or less prior to administration 2
   • Common diluents: 5% Dextrose Injection or 0.9% Sodium Chloride Injection 2

2. Maintenance Therapy:

   • IV magnesium sulfate 2 grams at least twice daily to maintain levels above 2.0 mg/dL 3
   • Monitor serum magnesium levels every 6-12 hours initially, then daily 1

Severe Hypomagnesemia:

1. Initial Treatment:

   • IV magnesium sulfate 2 grams over 20 minutes 1
   • For profound deficiency: up to 250 mg/kg body weight may be given IM within 4 hours 2
   • Alternative: 5 grams (40 mEq) added to 1L of IV fluid for slow infusion over 3 hours 2

2. Maintenance Therapy:

   • Continue IV replacement until serum levels normalize
   • Transition to oral therapy when clinically appropriate

Monitoring and Safety Considerations

• ECG Monitoring: Recommended during IV magnesium administration, especially for rapid infusion 1
• Rate Limitations: IV injection rate should generally not exceed 150 mg/minute 2
• Target Serum Level: >0.6 mmol/L (>1.5 mg/dL) 1
• Renal Function: Patients with renal dysfunction require careful monitoring due to risk of hypermagnesemia 1, 2
• Duration: Continuous maternal administration of magnesium sulfate in pregnancy should not exceed 5-7 days 1, 2

Transition to Oral Therapy

• Once stabilized, transition to oral magnesium supplementation:
  • Prefer organic magnesium salts (aspartate, citrate, lactate) at 400-500 mg daily due to superior bioavailability 1
  • Divide doses throughout the day to improve tolerance and absorption 1
  • Oral magnesium oxide provides a consistent median increase in serum magnesium of 0.1 mg/dL when baseline levels are 1.4-1.8 mg/dL 4

Common Pitfalls and Caveats

• IV administration results in greater and more rapid elevations in serum magnesium compared to oral administration 4
• Serum magnesium levels drop below 2.0 mg/dL within 24 hours of a single dose administration 3
• Diarrhea is the most common dose-limiting side effect of oral magnesium supplementation 1
• Alcoholic patients may have normal serum magnesium despite intracellular deficiency 1
• Concomitant use of IV loop diuretics significantly influences changes in serum magnesium concentration 4
• Continuous ECG monitoring is essential during IV magnesium administration to detect signs of toxicity 1

By following this protocol, hospitalized patients with magnesium deficiency can be effectively treated while minimizing risks of under or over-replacement.