What is the treatment for hypermagnesemia?

Treatment of Hypermagnesemia

Intravenous calcium administration is the first-line treatment for hypermagnesemia, particularly in patients with cardiac manifestations or severe toxicity, using either calcium chloride 10% (5-10 mL) or calcium gluconate 10% (15-30 mL) IV over 2-5 minutes. 1, 2

Immediate Management

Calcium Administration (First-Line)

• Administer IV calcium immediately for symptomatic hypermagnesemia or cardiac arrest, as calcium acts as a direct antagonist to magnesium's effects on the cardiovascular and neuromuscular systems 1, 2
• Calcium chloride 10%: 5-10 mL IV over 2-5 minutes 1, 3
• OR calcium gluconate 10%: 15-30 mL IV over 2-5 minutes 1, 3
• This is a Class IIb recommendation from the American Heart Association for cardiac arrest associated with hypermagnesemia 1
• Important caveat: Calcium antagonizes magnesium's toxic effects but does not reduce serum magnesium levels, so additional interventions are required 2

Discontinue Magnesium Sources

• Immediately stop all magnesium-containing medications including antacids (magnesium hydroxide), laxatives (magnesium salts), and IV magnesium therapy 2, 4
• Magnesium salts used for constipation can cause severe hypermagnesemia, especially in patients with renal impairment or prolonged colonic retention 1, 5

Definitive Treatment Based on Severity

Gastrointestinal Decontamination

• For patients who ingested magnesium-containing products (especially with constipation or bowel obstruction), use magnesium-free laxatives to remove retained magnesium from the GI tract 6
• This is critical because retained magnesium tablets in the colon cause continuous absorption and rebound hypermagnesemia even after initial treatment 6
• Failure to perform adequate GI decontamination can result in persistent toxicity despite dialysis 6

Intravenous Fluid Therapy

• Administer IV fluids to promote renal excretion of magnesium in patients with preserved renal function 7, 8
• Consider adding furosemide to enhance magnesium excretion 8

Renal Replacement Therapy

• Initiate hemodialysis or continuous renal replacement therapy (CRRT) for severe hypermagnesemia (typically >4-5 mEq/L) or when conservative measures fail 7, 5
• Hemodialysis is particularly indicated for patients with renal impairment, cardiac arrest, or life-threatening symptoms 7, 5
• Dialysis should be considered promptly rather than delayed, as it is the only method that actually removes magnesium from the body 7, 4
• One case report demonstrated successful recovery with hemodialysis after calcium and fluids failed 7

High-Risk Populations Requiring Aggressive Monitoring

• Obstetric patients receiving IV magnesium sulfate for preeclampsia/eclampsia are at highest risk for iatrogenic hypermagnesemia 3, 2
• Patients with end-stage renal disease or any degree of renal impairment taking magnesium-containing laxatives 1, 5
• Patients with normal renal function can still develop fatal hypermagnesemia if they have bowel obstruction, prolonged colonic retention, or excessive magnesium intake 5, 8

Critical Pitfalls to Avoid

• Do not rely solely on calcium administration—it provides temporary symptomatic relief but does not eliminate magnesium from the body 2
• Do not overlook GI decontamination in patients who ingested magnesium products, as incomplete removal leads to rebound hypermagnesemia 6
• Do not delay dialysis in severe cases or when initial supportive measures (calcium, fluids) are ineffective, as this can result in fatal outcomes 7, 5
• Monitor for cardiovascular collapse (bradycardia, hypotension, arrhythmias) and respiratory failure (hypoventilation), which can progress rapidly to cardiorespiratory arrest 1, 3