From the FDA Drug Label
In the treatment of mild magnesium deficiency, the usual adult dose is 1 g, equivalent to 8. 12 mEq of magnesium (2 mL of the 50% solution) injected IM every six hours for four doses (equivalent to a total of 32.5 mEq of magnesium per 24 hours). For severe hypomagnesemia, as much as 250 mg (approximately 2 mEq) per kg of body weight (0. 5 mL of the 50% solution) may be given IM within a period of four hours if necessary. Alternatively, 5 g (approximately 40 mEq) can be added to one liter of 5% Dextrose Injection, USP or 0. 9% Sodium Chloride Injection, USP for slow IV infusion over a three-hour period.
The appropriate dose of magnesium to administer to an inpatient with hypomagnesemia (magnesium level of 1.6) is 1 g (8.12 mEq) IM every 6 hours for 4 doses for mild deficiency, or up to 250 mg (2 mEq) per kg of body weight IM within 4 hours for severe hypomagnesemia. Alternatively, 5 g (40 mEq) can be added to 1 liter of 5% Dextrose Injection or 0.9% Sodium Chloride Injection for slow IV infusion over 3 hours 1.
- Key considerations:
- Severe hypomagnesemia: up to 250 mg (2 mEq) per kg of body weight IM within 4 hours
- Mild magnesium deficiency: 1 g (8.12 mEq) IM every 6 hours for 4 doses
- IV infusion: 5 g (40 mEq) in 1 liter of 5% Dextrose Injection or 0.9% Sodium Chloride Injection over 3 hours
From the Research
For a patient with a magnesium level of 1.6 mg/dL, I recommend administering 4-6 grams of magnesium sulfate intravenously over 24 hours, divided into multiple doses, as this approach is supported by the most recent and highest quality study 2.
Key Considerations
- The patient's magnesium level is below the normal range, indicating hypomagnesemia, which can lead to various complications such as cardiac arrhythmias and neuromuscular symptoms.
- The study by 2 found that intravenous administration of 1 g of MgSO4 results in a rise of serum magnesium levels by 0.1 mg/dL in patients with normal eGFR and around 0.15 mg/dL in patients with eGFR values between 30 and 89 mL/min/1.73 m2.
- Another study 3 evaluated the effectiveness and safety of magnesium replacement in critically ill patients and found that the target serum magnesium concentration was achieved in only 59.8% of episodes, highlighting the need for careful monitoring and adjustment of magnesium replacement.
Administration Guidelines
- Each dose of magnesium sulfate should be diluted in 50-100 mL of compatible IV fluid.
- Monitor the patient for signs of hypermagnesemia during administration, including hypotension, flushing, and decreased deep tendon reflexes.
- Continuous cardiac monitoring is advisable during IV administration.
- The goal is to achieve a normal magnesium level of 1.8-2.4 mg/dL.
Importance of Correcting Hypomagnesemia
- Magnesium is essential for numerous physiological processes, including neuromuscular function, cardiac conduction, and enzyme activities.
- Correcting hypomagnesemia is particularly important as it can exacerbate hypocalcemia and hypokalemia and may contribute to cardiac arrhythmias and neuromuscular symptoms, as noted in studies such as 4 and 5.