MIMS Revision Date: 01 March 2026

1 Name of Medicine

Magnesium sulfate heptahydrate.

2 Qualitative and Quantitative Composition

Magnesium Sulfate Baxter Ready to Use is available in two strengths:
Magnesium Sulfate Baxter Ready to Use contains 4 g magnesium sulfate heptahydrate in a 50 mL Viaflo plastic bag (8% w/v). Each 1 mL of solution contains 80 mg of magnesium sulfate heptahydrate; or 0.32 mmol of magnesium ions and 0.32 mmol of sulfate ions. The solution has an approximate osmolality of 357 mOsmol/kg and is considered Hypertonic.
Magnesium Sulfate Baxter Ready to Use contains 4 g magnesium sulfate heptahydrate in a 100 mL Viaflo plastic bag (4% w/v). Each 1 mL of solution contains 40 mg of magnesium sulfate heptahydrate; or 0.16 mmol of magnesium ions and 0.16 mmol of sulfate ions. The solution has an approximate osmolality of 189 mOsmol/kg and is considered Hypotonic.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Solution for intravenous infusion.
Magnesium Sulfate Baxter Ready to Use is a clear, colourless, sterile solution free from visible particles with a pH ranging between 3.5 and 6.5.
Magnesium Sulfate Baxter Ready to Use injection solution does not require dilution prior to use.

4 Clinical Particulars

4.1 Therapeutic Indications

Parenteral administration of Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion is indicated for the prevention and treatment of life-threatening seizures in the treatment of toxaemias of pregnancy (pre-eclampsia and eclampsia).

4.2 Dose and Method of Administration

An initial intravenous dose of 4 g of magnesium sulfate heptahydrate is recommended, and administered in accordance with hospital protocol/guideline. This is followed by an infusion of 1 to 2 g/hour.
The dose of magnesium should be adjusted according to the patient's individual requirements and response. Dosage should be reduced in renal impairment. The total adult daily dose should not exceed 30 to 40 g of magnesium sulfate heptahydrate per day.
Careful monitoring of plasma magnesium and other electrolyte concentration is essential whenever using this preparation. An intravenous preparation of a calcium salt should always be available in case of toxicity.
Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion is a ready to use preparation for intravenous (IV) infusion, and does not require dilution prior to use. No additional medications or additives should be added to Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion prior to administration (see Section 6.2 Incompatibilities).
Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion is for single use in one patient on one occasion only, and contains no antimicrobial preservative. Any unused portion should be discarded.
Parenteral drug products should be inspected visually for particulate matter and discolouration prior to administration whenever solution and container permit. The solution should be clear and free from particles. Do not administer unless solution is clear and seal is intact.

4.3 Contraindications

Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion is contraindicated in patients with:
Heart block - since magnesium may exacerbate this condition.
Severe renal failure (creatinine clearance < 20 mL/min) - since there is an increased risk of hypermagnesaemia in these patients.
Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion should not be administered to pregnant women in the two hours prior to delivery, unless it is the only therapy available to prevent eclamptic seizures. There is a risk that the neonate will be born with hypermagnesaemia and depressed breathing.

4.4 Special Warnings and Precautions for Use

Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion may precipitate an acute myasthenic crisis. Sensitivity to parenteral magnesium has been reported.
Monitoring serum magnesium levels and the patient's clinical status is essential to avoid the consequences of overdosage in toxaemia. An intravenous preparation of a calcium salt (e.g. calcium gluconate) should be readily available for use when Magnesium Sulfate Baxter Ready to Use is given.
Use in renal impairment. Magnesium should be administered with caution in patients with impaired renal function, since the risk of hypermagnesaemia is increased in these patients. Dosage should be reduced in renal impairment.
Use in the elderly. No data available.
Paediatric use. No data available.
Effects on laboratory tests. Monitoring of serum magnesium levels is advised at periodic intervals during therapy to ensure that normal serum magnesium levels are not exceeded.
The patellar reflex should be tested prior to administering repeat doses of magnesium sulfate heptahydrate. Suppression of the reflex is an indication of magnesium intoxication.
Respiration rate should be determined and should be at least 16 per minute prior to each dose of magnesium sulfate heptahydrate, as respiratory depression is the most critical side effect of the medication.
Urine output should be monitored and should be at least 100 mL during the four hours preceding dosing, to ensure adequate excretion of magnesium.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Cardiac glycosides/digitalis. Magnesium salts should be administered with caution in patients treated with cardiac glycosides, since heart block may occur if calcium salts are required to treat magnesium toxicity (see Section 4.9 Overdose).
CNS depressants. Concurrent use of magnesium salts and CNS depressant drugs may result in an enhanced CNS depressant effect.
Neuromuscular blocking agents. Concurrent use of magnesium salts with neuromuscular blocking agents such as tubocurarine, suxamethonium and vecuronium may result in an excessive neuromuscular blockade.
Nifedipine. Concurrent use of magnesium sulfate heptahydrate and nifedipine may result in an exaggerated hypotensive response.
Drug induced renal losses of magnesium occur with the following drugs and drug classes: aminoglycosides, ciclosporin, amphotericin B, diuretics, cisplatin.
Also see Section 6.2 Incompatibilities.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility. No data available.
Use in pregnancy. (Category D)
Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion is administered to pregnant women to treat seizures associated with severe preeclampsia and eclampsia. However, increased paediatric mortality has been noted when it was used in pre-term labour.
Magnesium sulfate readily crosses the placenta. Foetal serum concentrations are approximately those of the mother. If magnesium sulfate heptahydrate is administered in the two hours preceding delivery, the neonate may be born with signs of hypermagnesaemia, including respiratory depression, and therefore Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion should not be given in the two hours preceding delivery unless it is the only therapy available to prevent or treat eclamptic seizures. Foetal heart rate should be monitored.
Bony abnormalities and congenital rickets have been reported in neonates born to mothers treated with parenteral magnesium sulfate heptahydrate for prolonged periods of time (5 to 7 days duration).
Magnesium sulfate should only be used in pregnancy where the benefit outweighs the risk.
Use in lactation. Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion should be used with caution in lactating patients. After intravenous administration, magnesium is distributed into breast milk, and the concentration of magnesium in the breast milk is approximately twice that in the maternal serum. Magnesium is cleared from the breast milk within 24 hours of the cessation of the infusion.

4.7 Effects on Ability to Drive and Use Machines

The effects of this medicine on a person's ability to drive and use machines were not assessed as part of its registration.

4.8 Adverse Effects (Undesirable Effects)

Excessive administration of magnesium sulfate heptahydrate may result in hypermagnesaemia. The signs of hypermagnesaemia may include drowsiness, nausea, vomiting, flushing, hypotension, sweating, hypothermia, circulatory collapse, bradycardia, muscle weakness, muscle paralysis, blurred or double vision, CNS depression and loss of reflexes.
More severe hypermagnesaemia may result in respiratory depression, respiratory paralysis, renal failure, coma, cardiac arrhythmias and cardiac arrest. Hypocalcaemia with tetany, secondary to hypermagnesaemia, has been reported.
Reporting suspected adverse effects. Reporting suspected adverse reactions after registration of the medicinal product is important. It allows continued monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions at www.tga.gov.au/reporting-problems.

4.9 Overdose

Clinical features. Hypermagnesaemia may occur when large doses of magnesium are given, especially in patients with renal failure. Signs of hypermagnesaemia include drowsiness, nausea, vomiting, flushing, hypotension, sweating, hypothermia, circulatory collapse, bradycardia, muscle weakness, muscle paralysis, blurred or double vision, CNS depression and loss of reflexes. More severe hypermagnesaemia may result in respiratory depression, respiratory paralysis, renal failure, coma, cardiac arrhythmias and cardiac arrest.
Disappearance of the patellar reflex is a useful clinical sign to detect the onset of magnesium intoxication.
Treatment. In the treatment of hypermagnesaemia, the following measures may be required:
blood pressure and respiratory support;
intravenous administration of 2.5 to 10 mmol calcium salts (such as calcium gluconate) reverses the effects of magnesium toxicity;
dialysis may be required, particularly if renal function is impaired;
if renal function is normal, adequate fluids should be given so that urine output is at least 60 mL/hr to assist removal of magnesium from the body;
physostigmine (0.5 to 1.0 mg subcutaneously) may be helpful, but routine use is not recommended due to the potential toxicity;
hypermagnesaemia in the newborn may require resuscitation and assisted ventilation as well as IV calcium.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action. Magnesium is the second most abundant cation of intracellular fluid. It is an essential cation in numerous enzymatic processes, and is necessary for several steps in glycolysis, the Krebs cycle and in protein and nucleic acid synthesis. It is thus vital for normal energy storage and transfer, skeletal development, nerve conduction and muscle contraction. Magnesium plays an important role in neurochemical transmission, and is essential for proper neurochemical functioning.
Magnesium has an anticonvulsant effect. It possibly has antiarrhythmic effects and a role in calcium homeostasis and bone mineralisation. There is conflicting evidence that the routine use of intravenous magnesium sulfate heptahydrate in the setting of acute myocardial infarction is beneficial.
Deficiency of magnesium is closely associated with other electrolyte disturbances, particularly hypocalcaemia and hypokalaemia. The specific symptoms of hypomagnesaemia are therefore difficult to determine, but may include nausea, vomiting, muscle weakness, neuromuscular dysfunction such as paraesthesia, tremor and cramp, tachycardia and cardiac arrythmias.
Clinical trials. No data available.

5.2 Pharmacokinetic Properties

The 95% confidence intervals for magnesium levels in healthy Australian subjects are: neonate 0.6 to 0.9 mmol/L, and adult 0.8 to 1.0 mmol/L.
Distribution. Approximately 50% of magnesium in the body is found in bone, with the majority of the remainder stored in muscle and soft tissue; 1% or less is contained in the extracellular compartment, of which approximately 33% is protein-bound, with a further 12% bound to anions.
Metabolism. No data available.
Excretion. Magnesium is primarily excreted in the urine, with small amounts excreted in faeces, saliva and breast milk. Over 90% of magnesium filtered by the kidneys is reabsorbed, mainly in the ascending limb of the Loop of Henle, with significant amounts also absorbed in the proximal and distal tubules. The clearance is proportional to the plasma magnesium concentration and the glomerular filtration rate.
The onset of action after intramuscular injection is about 1 hour and after intravenous injection is nearly immediate. The duration of action after intramuscular injection is 3 to 4 hours, and after intravenous injection is about 30 minutes.

5.3 Preclinical Safety Data

Genotoxicity. No data available.
Carcinogenicity. No data available.

6 Pharmaceutical Particulars

6.1 List of Excipients

Water for injections. Sulfuric acid or sodium hydroxide for pH adjustment as needed.

6.2 Incompatibilities

Magnesium sulfate is incompatible with calcium salts. Calcium sulfate may precipitate when calcium salts are mixed with magnesium sulfate in the same intravenous solution.
Magnesium salts have also been reported to be incompatible with alkali carbonates and bicarbonates and soluble phosphates.
Also see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions.
No additional medications or ingredients should be added to Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store below 25°C. Do not freeze.
Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion should be kept in its original sealed overpouch until ready to be used.

6.5 Nature and Contents of Container

Magnesium Sulfate Baxter Ready to Use injection for intravenous infusion solutions are supplied as 4 g in 50 mL (8% w/v) and 4 g in 100 mL (4% w/v) flexible plastic (polypropylene/polyamide/polyethylene) Viaflo bags. Each bag is enclosed in an overpouch, made of a transparent film on one side and opaque aluminium foil on the other.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of in accordance with local requirements.

6.7 Physicochemical Properties

Chemical structure. The molecular formula is MgSO₄.7H₂O. The molecular weight of the compound is 246.5.
CAS number. 10034-99-8.

7 Medicine Schedule (Poisons Standard)

Unscheduled.

Date of First Approval

28 March 2024

Summary Table of Changes