Symptoms and Management of Magnesium Toxicity

Kobi Nathan

Magnesium toxicity, or hypermagnesemia, can present with a range of symptoms that primarily affect the cardiovascular, neuromuscular, and central nervous systems.

Hypermagnesemia is uncommon and usually occurs in the context of renal insufficiency or excessive magnesium intake, such as from magnesium-containing medications or supplementation.

The clinical manifestations depend on the serum magnesium levels and the rate of increase.

In clinical practice, it is important to monitor serum magnesium levels and assess for these symptoms, especially in patients with renal insufficiency or those receiving magnesium-containing medications or supplements, as mentioned above.

Mild to Moderate Hypermagnesemia

Mild to moderate hypermagnesemia refers to an elevated serum magnesium concentration that is above the normal range but not high enough to cause severe symptoms or require aggressive treatment. 

The normal serum magnesium concentration in adults is typically between 1.7 to 2.4 mg/dL (0.7 to 1.0 mmol/L).

Mild hypermagnesemia is generally considered to be a serum magnesium level of 2.5 to 4.0 mg/dL, while moderate hypermagnesemia ranges from 4.0 to 6.0 mg/dL.

Mild to moderate hypermagnesemia typically presents with a range of symptoms that are primarily neuromuscular and cardiovascular in nature.

These symptoms can include:

Nausea and vomiting: Gastrointestinal symptoms are common in mild to moderate cases.

Facial flushing: This can occur due to vasodilation (dilation of the blood vessels).

Hypotension: Mild to moderate hypermagnesemia can cause a drop in blood pressure.

Lethargy and drowsiness: Patients may experience a general sense of fatigue and decreased alertness.

Diminished deep tendon reflexes: Reflexes may be reduced, but not absent, in mild to moderate cases.

Muscle weakness: This can range from mild to moderate in severity.

These symptoms are generally less severe than those seen in severe hypermagnesemia, which can include more pronounced cardiovascular and neuromuscular effects such as bradycardia (low heart rate), respiratory depression, and cardiac arrest (more on this later).


Moderate to High Hypermagnesemia

Moderate to high hypermagnesemia refers to elevated levels of serum magnesium that can lead to significant clinical symptoms and complications.

The normal serum magnesium concentration in adults is 1.7 to 2.4 mg/dL (0.7 to 1.0 mmol/L).

Hypermagnesemia is typically classified based on serum magnesium levels:

Moderate hypermagnesemia: Serum magnesium levels between 2.5 to 5.0 mg/dL (1.0 to 2.0 mmol/L).

High hypermagnesemia: Serum magnesium levels above 5.0 mg/dL (2.0 mmol/L).

Moderate to high hypermagnesemia can present with a range of symptoms that primarily affect the neuromuscular and cardiovascular systems.

Neuromuscular symptoms include:
  • Hyporeflexia or diminished deep tendon reflexes
  • Lethargy and confusion
  • Muscle weakness and flaccid paralysis
  • Respiratory depression in severe cases

Cardiovascular symptoms include:

  • Hypotension (treatment-resistant in severe cases)
  • Bradycardia (low heart rate; less than 50 beats/min)
  • Prolonged PR, QRS, and QT intervals on ECG (abnormal heart rhythm)
  • Potential cardiac arrest
Other systemic symptoms can include:

  • Nausea and vomiting
  • Facial flushing
  • Ileus (inability of the intestine to contract normally and move waste out of the body)

The management of mild to moderate or moderate to high hypermagnesemia involves several key steps:

Discontinuation of Magnesium Intake:

The first step is to stop any exogenous sources of magnesium, such as supplements or medications containing magnesium.

Intravenous Calcium:

Administration of intravenous calcium gluconate or calcium chloride is recommended to antagonize the effects of hypermagnesemia on the cardiovascular and neuromuscular systems.

This is particularly important in cases presenting with severe symptoms such as hypotension, bradycardia, or respiratory depression.

Intravenous Fluids and Diuretics:

Aggressive intravenous hydration with isotonic saline can help enhance renal excretion of magnesium.

Loop diuretics, such as furosemide, may be used to promote diuresis and further increase magnesium excretion.

Dialysis:

In cases of severe hypermagnesemia, especially when there is renal insufficiency or when other measures fail to rapidly reduce magnesium levels, hemodialysis or continuous renal replacement therapy (CRRT) should be considered.

Dialysis is highly effective in rapidly lowering serum magnesium levels.

Monitoring and Supportive Care:

Continuous monitoring of cardiac and respiratory function is essential.

Supportive care, including mechanical ventilation, may be necessary in cases of respiratory depression.


In summary, the management of hypermagnesemia includes discontinuation of magnesium intake, administration of intravenous calcium, aggressive hydration with diuretics, and consideration of dialysis in severe cases. 

These steps are supported by clinical case reports and reviews in the medical literature.


References:

  1. Contemporary View of the Clinical Relevance of Magnesium Homeostasis. Ayuk J, Gittoes NJ. Annals of Clinical Biochemistry. 2014;51(Pt 2):179-88. doi:10.1177/0004563213517628.
  2. Clinical Implications of Disordered Magnesium Homeostasis in Chronic Renal Failure and Dialysis. Navarro-González JF, Mora-Fernández C, García-Pérez J. Seminars in Dialysis. 2009 Jan-Feb;22(1):37-44. doi:10.1111/j.1525-139X.2008.00530.x.
  3. Magnesium Disorders. Touyz RM, de Baaij JHF, Hoenderop JGJ. The New England Journal of Medicine. 2024;390(21):1998-2009. doi:10.1056/NEJMra1510603.
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  7. Unsuspected Morbid Hypermagnesemia in Elderly Patients. Clark BA, Brown RS. American Journal of Nephrology. 1992;12(5):336-43. doi:10.1159/000168469.
  8. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Panchal AR, Bartos JA, Cabañas JG, et al. Circulation. 2020;142(16_suppl_2):S366-S468. doi:10.1161/CIR.0000000000000916.
  9. Iatrogenic Acute Hypermagnesemia After Total Parenteral Nutrition Infusion Mimicking Septic Shock Syndrome: Two Case Reports. Ali A, Walentik C, Mantych GJ, et al. Pediatrics. 2003;112(1 Pt 1):e70-2. doi:10.1542/peds.112.1.e70.
  10. Acute Hypermagnesemia: A Rare Complication of Antacid Administration After Bone Marrow Transplantation. Jaing TH, Hung IJ, Chung HT, et al. Clinica Chimica Acta; International Journal of Clinical Chemistry. 2002;326(1-2):201-3. doi:10.1016/s0009-8981(02)00308-x.
  11. An Unusual Yet "Mg"nificent Indication for Hemodialysis. Bansal AD, Negoianu D, Warburton KM. Seminars in Dialysis. 2016;29(3):247-50. doi:10.1111/sdi.12479.
  12. Hemodialysis for Toxic Hypermagnesemia Caused by Intravenous Magnesium in a Woman With Eclampsia and Renal Insufficiency. A Case Report. Hirose M, Kobayashi M, Sudo S, Nakanishi K, Noda Y. The Journal of Reproductive Medicine. 2002;47(12):1050-2.
  13. Case Report: Near-Fatal Hypermagnesemia Resulting From the Use of Epsom Salts in a Patient With Normal Renal Function. Si GF, Ge YX, Lv XP, et al. Frontiers in Medicine. 2024;11:1416956. doi:10.3389/fmed.2024.1416956.
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