Treatment
- Oral magnesium salts
- IV or IM magnesium sulfate for severe hypomagnesemia or inability to tolerate or adhere to oral therapy
Treatment with magnesium salts is indicated when magnesium deficiency is symptomatic or the magnesium concentration is persistently < 1.25 mg/dL (< 0.50 mmol/L). Patients with alcohol use disorder are treated empirically. In such patients, deficits approaching 12 to 24 mg/kg are possible.
About twice the amount of the estimated deficit should be given in patients with intact renal function because about 50% of the administered magnesium is excreted in the urine. Oral magnesium salts (e.g. magnesium gluconate 500 to 1000 mg orally three times a day) are given for 3 to 4 days. The onset of diarrhea limits oral treatment.
Parenteral administration is reserved for patients with severe, symptomatic hypomagnesemia who cannot tolerate oral drugs. Sometimes a single injection is given in patients with alcohol use disorder who are unlikely to adhere to ongoing oral therapy. When magnesium must be replaced parenterally, a 10% magnesium sulfate solution (1 g/10 mL) is available for IV use, and a 50% solution (1 g/2 mL) is available for IM use. The serum magnesium concentration should be monitored frequently during magnesium therapy, particularly when magnesium is given to patients with renal insufficiency or in repeated parenteral doses. In these patients, treatment is continued until a normal serum magnesium concentration is achieved.
In severe, symptomatic hypomagnesemia (eg, magnesium < 1.25 mg/dL [< 0.5 mmol/L] with seizures or other severe symptoms), 2 to 4 g of magnesium sulfate IV is given over 5 to 10 minutes. When seizures persist, the dose may be repeated up to a total of 10 g over the next 6 hours. In patients in whom seizures stop, 10 g in 1 L of 5% D/W (dextrose in water) can be infused over 24 hours, followed by up to 2.5 g every 12 hours to replace the deficit in total magnesium stores and prevent further drops in serum magnesium.
When serum magnesium is ≤ 1.25 mg/dL (< 0.5 mmol/L), but symptoms are less severe, magnesium sulfate may be given IV in 5% D/W at a rate of 1 g/hour as slow infusion for up to 10 hours. In less severe hypomagnesemia cases, gradual repletion may be achieved by administering smaller parenteral doses over 3 to 5 days until the serum magnesium concentration is normal.
Concurrent hypokalemia or hypocalcemia should be specifically addressed in addition to hypomagnesemia. These electrolyte disturbances are difficult to correct until magnesium has been replete. Additionally, hypocalcemia can be worsened by isolated treatment of hypomagnesemia with intravenous magnesium sulfate because sulfate binds ionized calcium. [4]
Reference:
[1] https://www.msdmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypomagnesemia
[2] https://www.msdmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypomagnesemia
[3] https://www.medicalnewstoday.com/articles/322191#symptoms
[4] https://www.msdmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypomagnesemia