MAGNESIUM SULPHATE

Magnesium sulphate injection may be administered by intramuscular or intravenous routes. Since intramuscular (IM) injections are painful, involve multiple punctures, and have no therapeutic advantage over the intravenous route, IM therapy should be used only when peripheral venous access is impossible.

5ml/minute of a 10% solution or its equivalent. Dosage should be reduced in renal impairment. Plasma magnesium concentrations should be monitored throughout therapy Adults The dosage should be individualised according to patient’s needs and responses.

Mild magnesium deficiency 1g intramuscularly every 6 hours for 4 doses. Severe magnesium deficiency Up to 250mg/kg intramuscularly given within a period of 4 hours or 5g/litre of infusion solution intravenously over 3 hours. Children It is recommended that the solution be diluted to 20% w/v prior to intramuscular injection.

For intravenous administration, it is recommended in children and infants that magnesium sulphate be given as a 1% (10 milligrams per milliliter) solution intravenously over 1 hour. In severe conditions, it has been suggested to administer half of the dose during the first 15 to 20 minutes.

Up to a 3% magnesium sulphate solution has been suggested for intravenous use in severe conditions. Hypomagnesemia; Treatment and Prophylaxis Neonates, magnesium sulfate 25 to 50 mg/kg IV every 8 to 12 hours for 2 to 3 doses Children, magnesium sulfate 25 to 50 mg/kg IV every 4 to 6 hours for 3 to 4 doses; MAX single dose is 2000 mg.

Elderly No special recommendations except in renal impairment.

Hypersensitivity reactions. Hypocalcaemia. Hypermagnesaemia characterised by flushing, thirst, hypotension, drowsiness, nausea, vomiting, confusion, slurred speech, double vision, loss of tendon reflexes due to neuromuscular blockade, muscle weakness, respiratory depression, electrolyte/fluid abnormalities (hypophosphatemia, hyperosmolar dehydration), ECG changes (prolonged PR, QRS and QT intervals), bradycardia, cardiac arrhythmias, coma and cardiac arrest.

There is a risk of respiratory depression if magnesium sulphate is administered concomitantly with high doses of barbiturates, opioids or hypnotics (see ‘Interactions’).

Magnesium sulphate must be used with caution in patients suspected of or known to have renal impairment. Magnesium sulphate should not be used in hepatic coma if there is a risk of renal failure. Parenteral magnesium salts should be used with caution in patients with myasthenia gravis.

Serum calcium levels should be routinely monitored in patients receiving magnesium sulphate.

Hypersensitivity to magnesium and it salts. Magnesium sulphate is contraindicated in patients with heart block, myocardial damage or severe impaired renal function.