Formulary
Magnesium sulfate: Indications, Dosing, Side Effects and Interactions
Magnesium sulfate clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 4 min read
Magnesium sulfate: Indications, Dosing, Side Effects and Interactions
Magnesium sulfate clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**Severe acute asthma,Continuing respiratory deterioration in anaphylaxis**
- **Child** (By Intravenous Infusion): 2-17 years 40 mg/kg (max. per dose 2 g), to be given over 20 minutes.
- **Adult** (By Intravenous Infusion): 1.2-2 g, to be given over 20 minutes.
**Hypomagnesaemia**
- **Adult** (By Intravenous Infusion, Or By Intramuscular Injection): Up to 40 g, given over a period of up to 5 days, dose given depends on the amount required to replace the deficit (allowing for urinary losses).
**Hypomagnesaemia maintenance (e.g. in intravenous nutrition)**
- **Adult** (By Intravenous Infusion, Or By Intramuscular Injection): 2.5-5 g daily, usual dose 3 g daily.
**Emergency treatment of serious arrhythmias**
- **Adult** (By Intravenous Injection): 2 g, to be given over 10-15 minutes, dose may be repeated once if necessary.
**Rapid bowel evacuation (acts in 2-4 hours)**
- **Adult** (By Mouth): 5-10 g, dose to be mixed in a glass of water, taken preferably before breakfast.
**Severe acute asthma, Continuing respiratory deterioration in anaphylaxis for magnesium sulfate**
- **Child 2-17 years** (By intravenous infusion): 40 mg/kg (max. per dose 2 g), to be given over 20 minutes.
**Persistent pulmonary hypertension of the newborn for magnesium sulfate**
- **Neonate** (Initially by intravenous infusion): Initially 200 mg/kg for 1 dose, to be given over 20-30 minutes, then (by continuous intravenous infusion) 20-75 mg/kg/hour for up to 5 days if response occurs after initial dose, dose adjusted to maintain plasma magnesium concentration between 3.5-5.5 mmol/ litre.
**Hypomagnesaemia for magnesium sulfate**
- **Neonate** (By intravenous injection): 100 mg/kg every 6-12 hours as required, to be given over at least 10 minutes.
- **Child 1 month-11 years** (By intravenous injection): 50 mg/kg every 12 hours as required, to be given over at least 10 minutes.
- **Child 12-17 years** (By intravenous injection): 1 g every 12 hours as required, to be given over at least 10 minutes.
**Hypomagnesaemia maintenance (e.g. in intravenous nutrition) for magnesium sulfate**
- **Child** (By intravenous infusion, or by intramuscular injection): 50-100 mg/kg daily; maximum 5 g per day.
**Neonatal hypocalcaemia for magnesium sulfate**
- **Neonate** (By deep intramuscular injection, or by intravenous infusion): 100 mg/kg every 12 hours for 2-3 doses.
**Torsade de pointes for magnesium sulfate**
- **Child** (By intravenous injection): 25-50 mg/kg (max. per dose 2 g), to be given over 10-15 minutes, dose may be repeated once if necessary (consult local protocol).
Cautions
With oral use In rapid bowel evacuation-elderly and debilitated patients (in adults)
Contraindications
With oral use In rapid bowel evacuation-acute gastro-intestinal conditions (in adults)
Side effects
Rare or very rare With oral use Paralytic ileus (in adults) Frequency not known With intravenous use Bone demineralisation (reported in neonates following prolonged or repeated use in pregnancy); electrolyte imbalance; osteopenia (reported in neonates following prolonged or repeated use in pregnancy) With oral use Diarrhoea (in adults); gastrointestinal discomfort (in adults); hypermagnesaemia (in adults) Overdose Symptoms of hypermagnesaemia may include nausea, vomiting, flushing, thirst, hypotension, drowsiness, confusion, reflexes absent (due to neuromuscular blockade), respiratory depression, speech slurred, diplopia, muscle weakness, arrhythmias, coma, and cardiac arrest.
Interactions
**Other interactions (2):**
- Calcium channel blockers such as nifedipine or nimodipine may rarely lead to a calcium ion imbalance and could result in abnormal muscle function.
- Nifedipine: profound hypotension was produced in two women who were given oral Nifedipine.
Pregnancy
Important safety information For magnesium sulfate MHRA/CHM advice: Magnesium sulfate: risk of skeletal adverse effects in the neonate following prolonged or repeated use in pregnancy (May 2019) Maternal administration of magnesium sulfate for longer than 5-7 days in pregnancy has been associated with hypocalcaemia, hypermagnesaemia, and skeletal side-effects in neonates. Healthcare professionals are advised to consider monitoring neonates for abnormal calcium and magnesium levels, and skeletal side-effects if maternal treatment with magnesium sulfate during pregnancy is prolonged or repeated beyond current recommendations.
Hepatic impairment
Avoid in hepatic coma if risk of renal failure.
Renal impairment
With intramuscular use or intravenous use: Caution in mild to moderate impairment; avoid in severe impairment (increased risk of toxicity). M With oral use in adults: Avoid. M Dose adjustments With intramuscular use or intravenous use: Reduce dose (consult product literature). M
Medicinal forms
Capsule,Solution,Solution,Powder
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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