From the Guidelines
The patient with hypomagnesemia (magnesium level 0.78) should be treated with oral magnesium oxide 12-24 mmol daily, given at night to maximize absorption, as the first line of treatment. This approach is based on the guidelines for management of patients with a short bowel, which recommend correcting water and sodium depletion, and using oral magnesium preparations to treat hypomagnesemia 1. The use of magnesium oxide is preferred due to its high elemental magnesium content and solubility in dilute acid, which allows for better absorption in the stomach 1.
Key considerations for treatment include:
- Correcting water and sodium depletion to address secondary hyperaldosteronism 1
- Using oral magnesium oxide 12-24 mmol daily, given at night to maximize absorption 1
- Monitoring serum calcium levels if oral 1-alpha hydroxy-cholecalciferol is used to improve magnesium balance, to avoid hypercalcaemia 1
- Considering intravenous or subcutaneous infusion of magnesium if oral supplements do not normalize magnesium levels 1
It is essential to address the underlying cause of hypomagnesemia, whether it's medication-induced, malabsorption, or other conditions, to prevent recurrence and ensure effective treatment. Renal function should also be assessed before treatment, as magnesium is primarily excreted by the kidneys, and dosing should be adjusted accordingly to prevent hypermagnesemia.
From the Research
Treatment of Hypomagnesemia
To treat hypomagnesemia, the following steps can be taken:
- Determine the underlying cause of the hypomagnesemia, such as inadequate magnesium intake, increased gastrointestinal or renal losses, or redistribution from extracellular to intracellular space 2
- Measure fractional excretion of magnesium and urinary calcium-creatinine ratio to assess renal magnesium handling 2
- Treat asymptomatic patients with oral magnesium supplements 2
- Reserve parenteral magnesium for symptomatic patients with severe magnesium deficiency (< 1.2 mg/dL) 2
Replacement Methods
Different methods can be used to replace magnesium, including:
- Oral magnesium preparations for chronic use 3
- Intravenous or intramuscular magnesium sulfate for urgent correction of hypomagnesemia 3
- Subcutaneous magnesium sulfate for long-term management in ambulatory patients 4
- Intravenous magnesium and oral magnesium and calcium replacement for patients with symptomatic hypomagnesemia due to short bowel syndrome and PPI therapy 5
Considerations
When treating hypomagnesemia, consider the following:
- Establishment of adequate renal function is required before administering any magnesium supplementation 2
- Magnesium balance depends on intake and renal excretion, which is regulated mainly in the thick ascending limb of the loop of Henle 3
- Hypomagnesemia may result from gastrointestinal losses or renal losses, the latter due to primary renal magnesium wasting or in association with sodium loss 3
- Routine supplementation with intravenous magnesium sulphate can prevent symptomatic hypomagnesaemia associated with cis-platinum therapy 6