From the FDA Drug Label
DOSAGE & ADMINISTRATION ... Therapy should continue until paroxysms cease In Pre-eclampsia or Eclampsia ... A total daily (24 hr) dose of 30 to 40 g should not be exceeded. The maximum hour for neuroprotection by MgSO4 is not directly stated, but the total daily dose should not exceed 30 to 40 g and therapy should continue until paroxysms cease 1.
From the Research
Magnesium sulfate (MgSO4) for neuroprotection should not be administered for more than 24 hours maximum in clinical practice. The recommended regimen usually involves an initial loading dose followed by a maintenance infusion that continues for up to 24 hours after the initial event (such as preterm birth risk or eclampsia) 2. This 24-hour window appears to be the optimal duration for achieving neuroprotective effects while minimizing potential side effects. For preterm labor situations, administration typically begins when preterm birth is imminent and continues until delivery or for the maximum 24-hour period, whichever comes first. If delivery has not occurred after 24 hours and is no longer imminent, the infusion should be discontinued. The neuroprotective mechanism of MgSO4 involves blocking NMDA receptors, reducing calcium influx into neurons, decreasing excitotoxicity, and providing anti-inflammatory effects. These actions help protect the developing brain from injury during periods of hypoxia or ischemia. Extending treatment beyond 24 hours has not been shown to provide additional neuroprotective benefits and may increase the risk of adverse effects such as respiratory depression, hypotension, and other magnesium toxicity symptoms.
Some key points to consider when administering MgSO4 for neuroprotection include:
- The dose of 4 g given intravenously 15 min continued by 1 g/h until maximum 24 h and minimum for 4 h is the standard regiment proposed in most guidelines 2
- A total dose of 64 g was associated with the maximum protective effect, but other studies report on an increased risk of neonatal death with these high doses 2
- The combination of hypothermia and MgSO4 provided maximum protection to the neurovascular units, and this protective effect was mainly achieved through the regulation of Ca2+ homeostasis in different cells 3
- Prehospital initiation of magnesium sulfate therapy was safe and allowed the start of therapy within 2 hours after the onset of stroke symptoms, but it did not improve disability outcomes at 90 days 4
Overall, the evidence suggests that MgSO4 should be administered for a maximum of 24 hours to achieve optimal neuroprotective effects while minimizing potential side effects. The recommended regimen and dose should be carefully considered to ensure the best possible outcomes for patients.