Magnesium Sulphate (Obstetric — Eclampsia/Neuroprotection)

How it works

Magnesium acts as a membrane stabiliser and cerebral vasodilator and modulates NMDA receptor activity, raising the seizure threshold and conferring neuroprotective effects on the preterm fetal brain.

Prescribing in practice

• Magnesium toxicity is the key hazard, progressing from loss of deep tendon reflexes to respiratory depression and cardiac arrest, so administration requires monitoring of reflexes, respiratory rate and urine output, with calcium gluconate available as the antidote.
• It is given by a loading dose followed by a maintenance infusion under close supervision, with dose reduction considered in renal impairment as magnesium is renally cleared.
• Neonates born after recent maternal administration should be observed for hypotonia and respiratory depression.

Monitoring

Monitor deep tendon reflexes, respiratory rate and urine output during the infusion, escalating assessment if signs of toxicity appear.

Counselling the patient

• This medicine is given by drip to prevent fits and, when given early, to help protect a premature baby's brain.
• You may feel flushed, warm or nauseated while it runs.
• Staff will check your reflexes and breathing regularly to keep the dose safe.

Evidence & guidelines

The Magpie trial established magnesium sulphate as the agent of choice for preventing and treating eclampsia, and trial evidence supports its use for fetal neuroprotection in early preterm birth, as reflected in NICE guidance.