Magnesium Sulfate Injection

Magnesium Sulfate Injection

Available presentation(s): 10 mL. Verify the exact concentration and total active quantity on the prescription and dispensing label.

Introduction: Magnesium sulfate injection is used for magnesium replacement and specific obstetric and cardiac indications. It has a narrow safety margin when given rapidly or in renal impairment.

Dosage: Dose and rate depend on indication, serum magnesium, symptoms, renal function and concomitant therapy. Follow NZF/local protocols. Orders must specify elemental magnesium or magnesium sulfate clearly, plus dilution, rate and monitoring. The 500 mg/mL concentrate requires careful calculation.

Mechanisms of Action: Replaces magnesium, modulates neuromuscular transmission and calcium movement, stabilises excitable membranes and reduces acetylcholine release at high concentrations.

Contraindications & Precautions: Contraindications include heart block or myocardial damage where clinically relevant and severe renal failure without close monitoring. Monitor reflexes, respiratory rate, urine output, blood pressure and serum magnesium during high-dose therapy. Calcium gluconate should be available for toxicity management.

Interactions: Additive neuromuscular blockade with neuromuscular blockers; additive CNS/respiratory depression with sedatives; hypotension with calcium-channel blockers. Separate incompatible parenteral medicines.

Adverse Reactions / Side Effects: Flushing, warmth, nausea, hypotension, lethargy and local irritation are common dose/rate effects. Toxicity causes loss of reflexes, respiratory depression, bradycardia, heart block and cardiac arrest.

Pregnancy & Breastfeeding: Magnesium sulfate is used in pregnancy for established indications under obstetric protocols. Prolonged administration can affect fetal/neonatal bone and mineral status. It enters breast milk in small amounts; clinical use is generally compatible when indicated.

Storage: Store under the conditions stated on the Optimus dispensing label and product-specific worksheet. Protect from light where labelled. Do not freeze unless explicitly validated. Maintain cold chain if the label requires refrigeration. Do not use after the assigned beyond-use date or if there is visible particulate matter, precipitation, colour change, loss of container integrity or evidence of improper storage. Once entered, follow the validated in-use time; do not assume a compounded vial is multi-dose.

References

• New Zealand Formulary (NZF), current online edition; product-specific approved data sheets where available; USP Pharmaceutical Compounding—Sterile Preparations; and Optimus Healthcare validated formulation, sterility/endotoxin controls and assigned beyond-use date.
• DailyMed. Magnesium Sulfate Injection—prescribing information, current edition. https://dailymed.nlm.nih.gov/
• NIH Office of Dietary Supplements. Health Professional Fact Sheets (vitamins and minerals), current online editions. https://ods.od.nih.gov/factsheets/list-VitaminsMinerals/