From the Guidelines
For a condition requiring magnesium sulfate, the recommended dosage is a loading dose of 4 g IV or 10 g IM, followed by 5 g IM every 4 hours or an infusion of 1 g/h until delivery and for at least 24 hours postpartum, as indicated for preeclampsia prevention 1. The dosage of magnesium sulfate can vary depending on the specific condition being treated.
- For preeclampsia, the standard regimen is a loading dose of 4 g IV or 10 g IM, followed by 5 g IM every 4 hours or an infusion of 1 g/h until delivery and for at least 24 hours postpartum, as recommended by the ISSHP classification, diagnosis, and management recommendations for international practice 1.
- The ISSHP also recommends that all women with preeclampsia should receive MgSO4 for convulsion prophylaxis, especially in low-resource settings, where the cost-benefit is greatest 1. Key considerations for magnesium sulfate administration include careful monitoring for toxicity signs, such as decreased reflexes, respiratory depression, hypotension, and cardiac abnormalities, as well as assessment of renal function before administration and monitoring of serum magnesium levels during treatment, aiming for therapeutic ranges of 4-7 mg/dL for seizure prevention.
- The dosing regimens used in the Eclampsia and MAGPIE trials should be used, as recommended by the ISSHP 1. It is essential to note that the optimum time for delivery remains uncertain for women with gestational hypertension and no features of preeclampsia, and a consistent policy on the use of MgSO4 should be established in each unit, incorporating appropriate monitoring and assessment of maternal and fetal outcomes 1.
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.
The dosage of magnesium sulfate for a condition requiring it is 1 g for mild magnesium deficiency, and 250 mg (approximately 2 mEq) per kg of body weight for severe hypomagnesemia.
- The dose for mild magnesium deficiency is given IM every six hours for four doses.
- The dose for severe hypomagnesemia is given IM within a period of four hours if necessary 2.
From the Research
Dosage of Magnesium Sulfate
The dosage of magnesium sulfate can vary depending on the condition being treated. For severe preeclampsia, a loading dose of 4-6 grams is often administered, followed by a maintenance dose of 1-2 grams per hour 3, 4, 5.
- The maintenance dose of 1 gram per hour was found to be as effective as 2 grams per hour in preventing eclampsia, with fewer side effects 3.
- However, in overweight mothers with preeclampsia, a maintenance dose of 2 grams per hour was more effective in achieving therapeutic levels of magnesium 4.
- The therapeutic level of magnesium is generally considered to be between 4-8 mg/dL, although this can vary depending on the individual and the condition being treated 5, 6.
Administration Route
Magnesium sulfate can be administered intravenously or intramuscularly.
- A low-dose intravenous regimen (0.6 gm/h) was found to be equally effective as an intramuscular regimen in preventing convulsion recurrence and maternal deaths in women with eclampsia 7.
- The choice of administration route may depend on the individual patient's needs and the clinical setting.
Monitoring and Adjustment
It is important to monitor serum magnesium levels and adjust the dosage as needed to avoid toxicity.