Magnesium sulfate parenteral
- Drugs List
- Therapeutic Indications
- Dosage
- Administration
- Contraindications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
- Monograph
Presentation
Parenteral formulations containing magnesium sulfate.
Drugs List
Therapeutic Indications
Uses
Magnesium deficiency
Prevention of seizures in pre-eclampsia and eclampsia
Unlicensed Uses
Cardiac arrhythmias
Neonatal hypocalcaemia
Pulmonary hypertension of the newborn
Torsade de pointes
Treatment of acute severe asthma
Dosage
The dosage should be individualised according to patient's needs and responses. Plasma magnesium levels should be monitored throughout therapy.
Adults
Treatment of magnesium deficiency in hypomagnesaemia
IV administration
Up to a total of 40g (160mmol magnesium ions) by slow intravenous infusion of a diluted solution over up to 5 days.
Intramuscular administration (of a 50% w/v injection)
Mild magnesium deficiency: 1g magnesium sulfate (approximately 4mmol magnesium ions) intramuscularly every 6 hours for four doses.
Severe magnesium deficiency: up to 250mg/kg magnesium sulfate (approximately 1mmol/kg magnesium ions) intramuscularly given over four hours.
Prevention and control of seizures associated with severe pre-eclampsia and eclampsia
An initial intravenous loading dose of 4g to 5g magnesium sulfate (16mmol to 20mmol magnesium ions) followed by:
IV maintenance administration: 1g magnesium sulfate (4mmol magnesium ions) every hour, after the intravenous loading dose, for at least 24 hours after the last convulsion.
Intramuscular maintenance administration
5g magnesium sulfate (20mmol magnesium ions) immediately after the IV loading dose, usually in 50% solution, as deep intramuscular injection into the upper outer quadrant of each buttock (these injections are painful).
Maintenance therapy is a further 5g magnesium sulfate (20mmol magnesium ions) every 4 hours continued for 24 hours after the last fit (provided respiratory rate is greater than 16 per minute, urine output greater than 25ml per hour and knee jerks present).
Should seizures recur then give an additional intravenous dose of 2g to 4g magnesium sulfate (approximately 8mmol to 16mmol magnesium ions) over 5 minutes.
In women weighing less than 70kg: 2g magnesium sulfate (8mmol magnesium ions) over 5 minutes.
Treatment of cardiac arrhythmias (unlicensed)
2g magnesium sulfate (approximately 8mmol magnesium ions) by slow intravenous injection over 10 to 15 minutes. Repeat once if necessary.
Treatment of severe acute asthma and continuing respiratory deterioration in anaphylaxis (unlicensed)
1.2g to 2g magnesium sulfate by intravenous infusion over 20 minutes.
Children
Treatment of magnesium deficiency in hypomagnesaemia
The solution should be diluted to 20% w/v prior to intramuscular administration in children.
Alternative sources suggest the following doses:
Children aged 12 to 18 years: 4mmol magnesium ions (1g magnesium sulfate) 12 hourly as necessary by intravenous injection over at least 10 minutes.
Children aged 1 month to 12 years: 0.2mmol/kg magnesium ions (50mg/kg magnesium sulfate) 12 hourly as necessary by intravenous injection over at least 10 minutes.
Torsade de pointes (unlicensed)
Children aged 1 month to 18 years: 0.1mmol/kg to 0.2mmol/kg magnesium ions (25mg/kg to 50mg/kg magnesium sulfate) by intravenous injection over 10 to 15 minutes; maximum 8mmol magnesium ions (2g magnesium sulfate); dose repeated once if necessary.
Treatment of severe acute asthma and continuing respiratory deterioration in anaphylaxis (unlicensed)
Children aged 2 to 18 years: 40mg/kg magnesium sulfate (maximum 2g) by intravenous infusion over 20 minutes.
Neonates
Hypomagnesaemia
0.4mmol/kg magnesium ions (100mg/kg magnesium sulfate), by intravenous injection over at least 10 minutes, every 6 to 12 hours as necessary.
Neonatal hypocalcaemia (unlicensed)
0.4mmol/kg magnesium ions (100mg/kg magnesium sulfate) by deep intramuscular injection or intravenous infusion, 12 hourly for 2 to 3 doses.
Persistent pulmonary hypertension of the newborn (unlicensed)
Initially 200mg/kg magnesium sulfate by intravenous infusion over 20 to 30 minutes; if response occurs, then by continuous intravenous infusion of 20mg/kg/hour to 75mg/kg/hour (to maintain plasma magnesium concentration between 3.5mmol/litre to 5.5mmol/litre), given for up to 5 days.
Patients with Renal Impairment
In severe renal impairment the recommended dosage should not exceed 20mg (80mmols magnesium ions) in 48 hours.
Administration
For administration by intramuscular or intravenous routes.
For intravenous administration, a concentration of 20% or less should be used; the rate of injection not exceeding 1.5ml/minute of a 10% solution or its equivalent.
Contraindications
Acute renal failure
Atrioventricular block
Chronic renal failure
Hepatic encephalopathy
Hepatic impairment
Precautions and Warnings
Elderly
Breastfeeding
Myasthenia gravis
Pregnancy
Renal impairment
Respiratory disease
Reduce dose in patients with renal impairment
Not all available brands are licensed for all indications
Monitor blood pressure
Monitor ECG/blood pressure/toxicity/foetal heart when treating eclampsia
Monitor plasma concentrations of this drug
Monitor respiratory function
Monitor serum calcium levels
Monitor serum electrolytes
Neonate exposed in utero: Monitor Mg, Ca and skeletal adverse effects
During treatment monitor blood pressure, respiratory rate, urinary output and for signs of overdosage (loss of patellar reflexes, weakness, nausea, sensation of warmth, flushing, drowsiness, double vision, and slurred speech).
Magnesium sulfate should be administered with extreme caution in patients receiving digitalis therapy as cardiac conduction changes and heart block may occur.
Caution should be observed to prevent exceeding the renal excretory capacity .
Magnesium sulfate should not be used in hepatic coma if there is risk of renal failure.
A risk of respiratory depression if administered concomitantly with high doses of barbiturates, opioids or hypnotics.
Pregnancy and Lactation
Pregnancy
Use magnesium sulfate with caution during pregnancy.
Manufacturers advise to use in pregnancy only if considered essential.
If possible, magnesium sulfate should be avoided in pregnancy. Avoid within two hours of delivery as administration during labour may cause respiratory depression of the newborn infant. Magnesium sulfate can be used for appropriate indications such as pre-eclampsia and eclampsia, which may be life threatening to mother and baby (not all brands are licensed for this use).
Use of magnesium sulfate for longer than 5 to 7 days during pregnancy may increase the risk of skeletal adverse effects in the neonate. If magnesium sulfate is given repeatedly during pregnancy or for a prolonged period time, consider monitoring neonates for abnormal calcium and magnesium levels and skeletal adverse effects. Magnesium crosses the placenta and may produce hypotonia, hypoflexia, hypotension.
Lactation
Use magnesium sulfate with caution during breastfeeding.
Manufacturers advise to use in breastfeeding only if considered essential.
Side Effects
Arrhythmias
Bradycardia
Burning pain at injection site
Cardiac arrest
Cardiac arrhythmias
Coma
Confusion
Double vision
Drowsiness
ECG changes
Fluid and electrolyte disturbances
Flushing
Hypermagnesaemia
Hypersensitivity reactions
Hypocalcaemia
Hypophosphataemia
Hypotension
Hypotonia
Loss of deep tendon reflexes
Muscle weakness
Nausea
Osteopenia
Peripheral vasodilatation
Respiratory depression
Slurred speech
Thirst
Vomiting
Overdosage
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Further Information
Last Full Review Date: December 2019
Reference Sources
Summary of Product Characteristics: Magnesium Sulfate Injection 50% w/v Solution for Injection. Aurum Pharmaceuticals Ltd. Revised September 2019.
Summary of Product Characteristics: Magnesium Sulfate 1g/10ml Injection. Macarthys Laboratories Ltd. Revised September 2019.
Summary of Product Characteristics: Magnesium Sulfate 20% w/v solution for infusion. Synchrony Pharma Ltd. Revised June 2019.
Summary of Product Characteristics: Magnesium Sulfate Injection 50% w/v Solution for Injection or Infusion. Torbay and South Devon NHS Foundation Trust. Revised August 2019.
MHRA Drug Safety Update May 2019
Available at: https://www.mhra.gov.uk
Last accessed: 08 August 2019
NICE Evidence Services Available at: www.nice.org.uk Last accessed: 17 December 2019
Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
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