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IV/Vitamins

MAGNESIUM

Last updated 4/30/2026

MAGNESIUM

Magnesium sulfate heptahydrate (Phebra 5 g/10 mL injection solution) is a high-concentration preparation that requires dilution and careful dosing depending on indication. Below is a safe, evidence-based clinical dosing overview.

Hypomagnesemia (replacement therapy)

Dose: 1–2 g (2–4 mL) IV diluted, infused over 1–2 hours.

Frequency: Repeat every 6–12 hours as needed, or continuous infusion depending on severity.

Typical daily max: 4–8 g/day (unless severe deficiency under ICU setting).

Moderate Dose (Fatigue, Stress, Muscle Tension)

  • 2–4 g magnesium sulfate IV (≈ 200–400 mg elemental magnesium)
  • Diluted in 500 mL fluid
  • Infused over 45–90 minutes
  • Frequency: Weekly, or twice weekly in acute deficiency cases (under medical guidance).

Dilution & Administration

  • Always dilute in 500 mL compatible fluid depending on dose.
  • Infuse SLOWLY to avoid rapid administration → risk of hypotension, bradycardia, respiratory depression.
  • BP, HR, respiratory rate during infusion.
  • Deep tendon reflexes (loss may indicate toxicity).
  • Serum magnesium levels if ongoing therapy (target: 1.7–2.5 mmol/L in replacement; 2–3.5 mmol/L in eclampsia).
  • Renal function (Mg is renally excreted).

⚠ Antidote: Calcium gluconate 10% IV is used to reverse magnesium toxicity.

Clinical Notes

  • Give slowly → rapid IV magnesium causes hypotension, flushing, dizziness, or warmth in face/chest.
  • Always monitor: BP, HR, and patient comfort during infusion.
  • Adjust dose if patient has renal impairment (risk of accumulation).
  • Contraindications: severe renal failure, heart block, myasthenia gravis.

Summary for IV Vitamin Therapy Clinics:

  • Wellness: 1–2 g weekly
  • Moderate support: 2–4 g weekly
  • High/medical: 4–6 g weekly or biweekly (doctor-led)

References

Australian Injectable Drugs Handbook

https://aidh.hcn.com.au/browse/m/magnesium_sulfate

STABILITY

Ampoule and vial: store below 25 °C.1 Do not refrigerate.2

Infusion solution: stable for 24 hours below 25 °C.1

No Incompatibilities

REFERENCES

  1. Product information. Available from www.tga.gov.au. Accessed 25/01/2023.
  2. ASHP Injectable drug information 2021. Bethesda, MD: American Society of Health-System Pharmacists; 2021.
  3. Phelps SJ, Hagemann TM, Lee KR, Thompson AJ. Pediatric injectable drugs. The teddy bear book. 11th ed. Bethesda, MD: American Society of Health-System Pharmacists; 2018.
  4. Electrolyte abnormalities [March 2021]. In: Therapeutic Guidelines [internet]. Melbourne: Therapeutic Guidelines Limited; August 2022.
  5. Medical Information. Plasma-Lyte 148 compatibility summary. Toongabbie, NSW: Baxter; March 2022.
  6. Trissel LA, Leissing NC. Trissel's Tables of physical compatibility. Lake Forest IL: Multimatrix; 1996.
  7. Voirol P, Berger-Gryllaki M, Pannatier A, Eggimann P, Sadeghipour F. Visual compatibility of insulin aspart with intravenous drugs frequently used in ICU. Eur J Hosp Pharm 2014; 22: 123-4.
  8. Magnesium sulfate. In: IV index [internet]. Trissel's 2 clinical pharmaceutics database (parenteral compatibility). Ann Arbour, MI: Merative. Accessed 25/01/2023.