Composition
Inj: Each ml of the 50% solution contains 500 mg magnesium sulphate heptahydrate (approx 2 mmol magnesium per ml).
Indications & Dosage
Prevention of seizures in pre-eclampsia: BY IV INJ: Adult: Initially 4 g, to be given over 5-15 minutes, followed by (by IV INF) 1 gram/hour for24 hours, if seizure occurs, additional dose of 2g by IV injection to be administered; if seizure recurs, increase the INF rate to1.5-2 g/hour or give an additional dose of 2g by IV injection. Magnesium deficiency and hypomagnesaemia: BY IV INF, OR BY IM INJ: Adult: Up to 40 g, given over a period of up to 5 days, dose given depends on the amount required to replace the deficit (allowing for urinary losses); maintenance: 2.5-5 g daily, usual dose 3 g daily. Emergency treatment of serious arrhythmias: BY IV INJ: Adult: 2 g, to be given over 10-15 minutes, dose may be repeated once if necessary. Myocardial infarction: BY IV INJ, IV INF: Adults: Initially IV injection of 8 mmol magnesium over 20 min, followed by IV INF of 65-72m molof magnesium over the following 24 hr. Severe acute asthma, continuing respiratory deterioration in anaphylaxis: BY IV INF: Adult: 1.2-2 g, to be given over 20 minutes. Children 2-17 years: 40 mg/kg (max. per dose 2 g), to be given over 20 minutes.
Administration
Concentration of magnesium sulphate should not exceed 20% of dilution.
Compatibility
Stable in D5W, NS, mannitol, KCI.
Precautions
Renal impairment; avoid or reduce dose, increased risk of toxicity. Hepatic impairment; avoid in hepatic coma if risk of renal failure.Monitor magnesium and other electrolytes closely. Monitor blood pressure,respiratory rate, urinary output and for signs of over dosage (loss of patellar reflexes, weakness, nausea,sensation of warmth, flushing, drowsiness, double vision,and slurred speech).Excessive doses in third trimester of pregnancy cause neonatal respiratory depression.
Interactions
Calcium channel blockers, nifedipine, non-depolarising muscle relaxants, suxamethonium.
Side Effects
Arrhythmias, coma, confusion, drowsiness, flushing of skin, hypotension, loss of tendon reflexes, muscle weakness, nausea, respiratory depression, thirst, vomiting