From the Guidelines
Magnesium sulfate is the first-line medication for treating and preventing eclamptic seizures. The standard loading dose is 4-6 grams IV over 15-20 minutes, followed by a maintenance infusion of 1-2 grams per hour for 24 hours after the last seizure or delivery, whichever comes later, as recommended by recent guidelines 1. This treatment approach is supported by the American Journal of Obstetrics and Gynecology, which emphasizes the importance of magnesium sulfate in preventing and treating eclampsia.
Some key points to consider when administering magnesium sulfate include:
- Monitoring for signs of magnesium toxicity, such as loss of deep tendon reflexes, respiratory depression, and hypotension 1
- Having calcium gluconate (1 gram IV) readily available as an antidote for magnesium toxicity
- Understanding that magnesium works by blocking N-methyl-D-aspartate (NMDA) receptors and calcium channels in the brain, reducing neuronal excitability and preventing seizures
- Recognizing that magnesium also causes vasodilation, which helps reduce cerebral edema and lower blood pressure, addressing the underlying pathophysiology of eclampsia
If seizures persist despite magnesium therapy, other treatment options may be considered, such as benzodiazepines (e.g., lorazepam or diazepam) or anticonvulsants (e.g., phenytoin or levetiracetam) 1. However, magnesium sulfate remains the primary treatment for eclamptic seizures, and its use is widely recommended by international clinical practice guidelines 1.
From the FDA Drug Label
IV use in eclampsia should be reserved for immediate control of life-threatening convulsions. 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.
The medication for eclamptic seizure is magnesium sulfate (IV), which is used for the immediate control of life-threatening convulsions 2 and works by blocking neuromuscular transmission and decreasing the amount of acetylcholine liberated at the end-plate by the motor nerve impulse 2.
- The effective anticonvulsant serum levels of magnesium range from 2.5 to 7.5 mEq/L.
- The onset of anticonvulsant action with IV administration is immediate and lasts about 30 minutes 2.
From the Research
Medications for Eclamptic Seizure
- Magnesium sulfate is the primary medication used to prevent eclamptic seizures in patients with pre-eclampsia and eclampsia 3, 4, 5.
- It has been shown to be more effective than other medications such as diazepam, phenytoin, and benzodiazepines in preventing recurrent seizures in eclamptic patients 3, 4, 6.
- The dosage regimens of magnesium sulfate are empirical, and further studies are needed to establish the optimal dosage and to minimize the risk of adverse effects 3, 5.
- Phenytoin and benzodiazepines can be used as alternative medications for the treatment of eclampsia, but they are not as effective as magnesium sulfate 7, 4, 6.
- Levetiracetam is also considered a suitable second-line agent for the treatment of status epilepticus in pregnancy, including eclampsia 7.
Comparison of Medications
- A study comparing magnesium sulfate with phenytoin found that magnesium sulfate was superior in preventing eclampsia in hypertensive pregnant women 4.
- Another study comparing the anticonvulsant and tocolytic effects of magnesium sulfate and phenytoin found that magnesium sulfate was more effective in preventing convulsions, but phenytoin may be considered for treatment of mild preeclampsia 6.
- Magnesium sulfate has been shown to have a lower convulsion rate compared to phenytoin, and it also has a positive effect on infant Apgar scores 6.
Mechanism of Action
- The exact mechanism of action of magnesium sulfate in preventing eclampsia is not fully understood, but it is thought to involve its effects on peripheral and cerebral vasodilation, blood-brain barrier protection, and anticonvulsant action 5.
- Magnesium sulfate may act as a vasodilator, decreasing peripheral vascular resistance or relieving vasoconstriction, and it may also protect the blood-brain barrier and limit cerebral edema formation 5.