Drug Index

Magnesium Sulphate

Synonyms :

Bitter salts, Epsom salts

Mechanism :

Magnesium is the second most plentiful cation of the intracellular fluids. It is essential for the activity of many enzyme systems and plays an important role with regard to neurochemical transmission and muscular excitability. Deficits are accompanied by a variety of structural and functional disturbances.

Indication :

  • Neonatal hypocalcemia
  • Hypomagnesemia
  • Bronchodilator in asthma
  • Acute nephritis

Contraindications :

Magnesium sulfate should not be administered parenterally in patients with heart block or myocardial damage, diabetic coma or hypersensitivity.

Use with caution in renal failure.

Dosing :

Hypomagnesemia in newborn/refractory hypocalcemia:
IM/IV 25-50 mg/kg every 4-6 hours as and when needed.
25-50 mg/kg over 10-20 mins, intravenously.
Acute nephritis:
100 mg/kg IM every 4-6 hours, as needed, or 20-40 mg/kg IM as needed.

Adverse Effect :

Flushing, hypothermia, sweating, sharply lowered blood pressure, stupor, CNS depression with depressed reflexes and disorientation, dilated pupils and ultimately, respiratory depression. Electrocardiograph changes with a magnesium sulfate overdose have included increased QRS complex width, increased PR interval, and prolonged QT interval. Nervous system side effects from hypermagnesemia result from suppression of neuromuscular transmission in the CNS and at the neuromuscular junction by magnesium. Clinically, serum levels above 4 to 7 mEq/L have led to decreased deep tendon reflexes, muscle weakness, mental confusion or sedation. At levels of 7 to 10 mEq/L, slower respiratory rates and decreased blood pressure has been reported. At levels of 10 to 15 mEq/L, profound mental depression, areflexia, coma and respiratory paralysis has been a common occurrence. Magnesium has also been reported to have a curare-like effect at the neuromuscular junction at serum levels above 10 mEq/L. Death may occur at any serum level but has been especially common at levels above 15 mEq/L. Gastrointestinal side effects have included primarily diarrhea, nausea (Mg levels of 4 to 5 mEq/L), and rare cases of paralytic ileus (Mg levels greater than 5 mEq/L). Cardiovascular side effects of magnesium are due to vasodilation, leading to flushing, chest pain and palpitations with rapid infusions and hypotension at serum levels of 7 to 10 mEq/L. Bradyarrhythmia’s have occurred at levels above 10 mEq/L. Asystole has occurred at levels above 25 mEq/L. Others: pulmonary edema. Diplopia, urticarial rash

Interaction :


Amikacin, Tobramycin, Neomycin, Netilmicin, Kanamycin, Streptomycin, Gentamycin, Calcitriol.
Caution when using:

Atracurium, Botulinum toxin, Cisatracurium, Edrophonium, Neostigmine, Nifedipine, Pancuronium, Pyridostigmine, Rocuronium, Vecuronium.

Hepatic Dose :

No dosage adjustments are recommended. Avoid in hepatic coma if risk of renal failure.
03/23/2024 04:43:47 Magnesium Sulphate
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