From the Guidelines
Magnesium sulfate is effective in preventing eclampsia in preeclamptic women, with a significant reduction in seizure risk, as evidenced by the landmark MAGPIE trial and recommended by the ISSHP guidelines 1. The mechanism of action of magnesium sulfate in preeclampsia involves its role as a central nervous system depressant and vasodilator, which helps to reduce neuronal excitability and prevent seizures. Key benefits of magnesium sulfate in preeclampsia include:
- Prevention of eclampsia, with approximately 100 women needing treatment to prevent one seizure 1
- Mild vasodilation, potentially improving uteroplacental blood flow and lowering blood pressure slightly
- Recommendation by ISSHP for use in all preeclamptic women in low- and middle-income countries (LMICs) due to the significant cost-benefit ratio 1 The standard dosing regimen for magnesium sulfate involves a loading dose of 4-6 grams IV over 15-20 minutes, followed by a maintenance infusion of 1-2 grams per hour, typically continued for 24 hours after delivery or after the last seizure, as used in the Eclampsia and MAGPIE trials 1. During administration, patients require close monitoring of deep tendon reflexes, respiratory rate, urine output, and serum magnesium levels, with therapeutic levels between 4-7 mEq/L. It's essential to note that while magnesium sulfate prevents seizures, it doesn't cure preeclampsia itself, and definitive treatment requires delivery of the baby and placenta, as recommended by the ISSHP guidelines 1.
From the FDA Drug Label
Magnesium prevents or controls convulsions by blocking neuromuscular transmission and decreasing the amount of acetylcholine liberated at the end-plate by the motor nerve impulse. Magnesium acts peripherally to produce vasodilation With low doses only flushing and sweating occur, but larger doses cause lowering of blood pressure.
Magnesium sulfate works in preeclampsia by:
- Blocking neuromuscular transmission to prevent or control convulsions
- Producing vasodilation, which helps to lower blood pressure It is essential to note that the exact mechanism of action in preeclampsia is not fully explained in the provided drug labels, but the above points are the most relevant information available 2.
From the Research
Mechanism of Action of Magnesium Sulfate in Preeclampsia
- Magnesium sulfate (MgSO4) is the agent most commonly used for treatment of eclampsia and prophylaxis of eclampsia in patients with severe pre-eclampsia 3.
- The exact mechanism of action of MgSO4 in preeclampsia is not fully understood, but it is thought to have diverse cardiovascular and neurological effects, and also alters calcium metabolism 4.
- MgSO4 has been shown to decrease neuroinflammation and increase seizure threshold in a rat model of severe preeclampsia, potentially by protecting the blood-brain barrier and preventing neuroinflammation 5.
Clinical Effects of Magnesium Sulfate in Preeclampsia
- MgSO4 has been shown to more than halve the risk of eclampsia in women with pre-eclampsia, and probably reduces maternal death 6.
- MgSO4 also reduces the risk of placental abruption and increases the risk of caesarean section 6.
- The clinical effect and toxicity of MgSO4 can be linked to its concentration in plasma, with a concentration of 1.8 to 3.0 mmol/L suggested for treatment of eclamptic convulsions 3.
Comparison with Other Treatments
- MgSO4 has been compared to other anticonvulsants, such as phenytoin and nimodipine, and has been shown to be more effective in preventing eclampsia 6.
- MgSO4 has also been compared to labetalol and nifedipine in the treatment of preeclampsia, and has been shown to be effective in reducing blood pressure, but with a higher risk of side effects 7.