What is the treatment for magnesium toxicity?

Treatment of Magnesium Toxicity

The treatment of magnesium toxicity requires immediate administration of intravenous calcium (calcium chloride 10% 5-10mL or calcium gluconate 10% 15-30mL) as a physiological antagonist to counteract magnesium's effects. 1, 2

Clinical Manifestations and Assessment

• Mild-moderate toxicity (serum Mg 2.5-5 mmol/L) presents with nausea, flushing, headache, lethargy, diminished deep tendon reflexes, and ECG changes including prolonged PR, QRS, and QT intervals 2
• Severe toxicity (serum Mg 6-10 mmol/L) manifests as hypotension, bradycardia, respiratory depression, complete heart block, and potential cardiac arrest 2
• Magnesium toxicity can progress to areflexia and respiratory depression at high serum concentrations, though this risk is small with standard therapeutic doses used for torsades de pointes (1-2g IV) 1

Treatment Algorithm

First-Line Treatment:

• Administer IV calcium as an immediate antidote (calcium chloride 10% 5-10mL or calcium gluconate 10% 15-30mL IV over 2-5 minutes) 1, 2
• This calcium administration is considered Class IIb, LOE C according to American Heart Association guidelines for cardiac arrest associated with hypermagnesemia 1

Supportive Measures:

• Ensure adequate hydration with IV fluids to enhance renal magnesium excretion 2
• Monitor vital signs, cardiac rhythm (continuous ECG monitoring), and neurological status closely 2
• Assess deep tendon reflexes frequently as an indicator of magnesium toxicity 2

For Severe or Refractory Cases:

• Consider hemodialysis for patients with:
  • Severe symptoms unresponsive to calcium and supportive care
  • Renal impairment limiting magnesium excretion
  • Extremely high serum magnesium levels 2, 3

Special Considerations

• Patients with renal impairment are at higher risk for magnesium toxicity even with lower doses due to impaired excretion 2
• Iatrogenic magnesium overdose can occur in various settings, including obstetric patients receiving magnesium for preeclampsia/eclampsia and emergency department patients 4, 5
• Certain medications (diuretics, digoxin) may potentiate magnesium toxicity 2
• In cases of digoxin toxicity with ventricular arrhythmias, intravenous magnesium is often administered, but monitoring for signs of magnesium toxicity is essential 1

Monitoring and Follow-up

• Obtain serial serum magnesium levels to track response to treatment 2
• Continue monitoring cardiac function with ECG until magnesium levels normalize 2
• Assess renal function, as impaired kidney function can prolong hypermagnesemia 2
• Consider poison control center consultation for complicated cases 2

Pitfalls and Caveats

• Medication errors in magnesium administration are a significant risk due to varying units of measurement used in orders and on drug labels 4
• Always verify the correct dose and concentration before administering magnesium-containing products 4
• Be vigilant for signs of magnesium toxicity in patients receiving therapeutic magnesium, especially those with renal impairment 2
• Hypermagnesemia is relatively uncommon but potentially life-threatening if not promptly recognized and treated 6