Magnesium Sulfate

What it is and how it works

Magnesium is an essential cofactor for many enzymes and for membrane ion transport. Parenteral magnesium sulfate depresses neuromuscular transmission by reducing acetylcholine release, acts as a calcium antagonist and NMDA-receptor blocker, and has antiarrhythmic and bronchodilator effects.

Indications

Prevention and treatment of seizures in severe pre-eclampsia and eclampsia; treatment of magnesium deficiency (hypomagnesaemia); torsade de pointes; adjunct in acute severe asthma; fetal neuroprotection in preterm birth.

Dosage and administration (summary)

Eclampsia/pre-eclampsia: commonly 4 g by slow intravenous injection over 5–15 minutes, then 1 g/hour by infusion for 24 hours (regimens per protocol). Hypomagnesaemia: dose individualised by deficit and serum magnesium. Torsade de pointes: 2 g intravenously over 10–15 minutes. Acute severe asthma: 1.2–2 g by intravenous infusion over 20 minutes.

Contraindications

Heart block or myocardial damage; myasthenia gravis; severe renal impairment (unless serum levels are closely monitored); hepatic coma with risk of renal failure.

Warnings and precautions

Monitor patellar reflexes, respiratory rate, urine output and, where possible, serum magnesium; loss of reflexes and respiratory depression indicate toxicity, for which intravenous calcium gluconate is the antidote. Reduce dose and monitor closely in renal impairment. Potentiates neuromuscular blocking agents and may interact with calcium-channel blockers.

Pregnancy

Standard treatment in pre-eclampsia and eclampsia; continuous use for more than 5–7 days has been associated with fetal hypocalcaemia and skeletal abnormalities.

Storage and supply

Store below 25 °C; do not freeze.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.