Magnesium Sulfate Injectable: Eclampsia Dosing
Magnesium sulfate injectable guidance for severe pre-eclampsia and eclampsia with close monitoring requirements.
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Source reviewed
October 2024
Guide category
Injectable drugs
Safety boundary
Prescription medicine information for clinician-guided use.
Kenza Health Hub presents this medicine page as structured health education. Check dose, route, interactions, pregnancy or breast-feeding considerations, and local protocol with a qualified clinician or pharmacist. Read our medical editorial policy.
Therapeutic action
Calcium antagonist, anticonvulsant.
Indications
- Severe pre-eclampsia for prevention of eclamptic seizures.
- Eclampsia for treatment of eclamptic seizures and prevention of recurrence.
Forms and strengths, route of administration
This drug should only be used by well trained personnel in well-equipped hospitals. During and after administration, have ventilation equipment, calcium gluconate, and solutions for fluid replacement ready for use.
- 5 g ampoule (0.5 g/ml, 10 ml) for IM injection or IV infusion.
Dose and duration
Continue treatment for 24 hours after delivery or the last seizure.
If seizures persist or recur, administer a further 2 g in patients under 70 kg or 4 g by IV infusion, without exceeding 8 g total during the first hour.
Reduce the dose in patients with renal impairment and do not administer to patients with severe renal impairment.
IV/IM protocol
- 4 g by IV infusion in 100 ml of 0.9% sodium chloride over 15 to 20 minutes then 10 g by IM route, 5 g in each buttock, then 5 g by IM route every 4 hours, changing buttock for each injection.
IV protocol
- 4 g by IV infusion in 100 ml of 0.9% sodium chloride over 15 to 20 minutes then 1 g per hour by continuous IV infusion.
Contra-indications, adverse effects, precautions
- May cause pain at the injection site, warm flushes, and decreased foetal heart rate.
- In overdosage with hypermagnesaemia, the mother may develop diminished then absent patellar reflex, hypotension, drowsiness, confusion, difficulty in speaking, bradycardia, and respiratory depression.
- In neonates of treated mothers, hypotonia, neurobehavioural impairment, apnoea, and respiratory depression may occur.
- Do not combine with nifedipine.
- Check urine output every hour. If urine output is under 30 ml/hour or 100 ml/4 hours, stop magnesium sulfate and perform delivery as soon as possible.
- Check patellar reflex, blood pressure, heart rate, and respiratory rate every 15 minutes during the first hour, then every hour if no signs of overdose are observed.
- If signs of overdose are observed, stop magnesium sulfate and give 1 g calcium gluconate by slow IV route as an antidote.
- Breast-feeding: no contra-indication.
- Magnesium sulfate is also used as an adjunctive treatment in severe asthma attack in children and adults: 40 mg/kg, maximum 2 g, by IV infusion over 20 minutes.
- Also comes in ampoules containing 1 g and in many other dosages. Check the strength of the ampoule carefully before use.
- 1 g magnesium sulfate contains approximately 4 mmol (8 mEq) of magnesium.
- Do not mix with other drugs in the same syringe or infusion fluid.
Source
MSF Essential drugs practical guidelines (January 2026)
This page combines source-derived medicine reference sections with Kenza editorial context, while leaving out the Storage and Remarks sections from the source batch.
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