MAGNESIUM SULFATE

Posology Dosages should be adjusted according to the patient's needs, responses and weight. Plasma magnesium levels should also be monitored during treatment to determine the rate and duration of infusion. 8). The infusion rate should be reduced or stopped if the patient develops signs of changes to cardiac condition (ECG changes).

Treatment of magnesium deficiency in hypomagnesaemia:

Treatment should be given via an infusion pump and an infusion rate of 1 g magnesium sulfate (5 mL of a 20% w/v solution equivalent to 4 mmol of magnesium ions) per hour is recommended, with a maximum rate of 2 g magnesium sulfate (10 mL of a 20% w/v solution approximately 8 mmol magnesium ions) per hour (not exceeding 28 g in 24 hours).

Higher infusion rates may be given in the management of emergencies. Up to 40 g (200 mL of a 20% w/v solution equivalent to 160 mmol of magnesium ions) by slow intravenous infusion (in glucose 5% w/v) given over a period of up to 5 days, may be required to replace the deficit (allowing for urinary losses).

9% w/v over 6 hours may be considered.

Prevention and control of seizures in severe pre-eclampsia:

An intravenous loading dose of typically 4 g (20 mL of a 20% w/v solution equivalent to 16 mmol of magnesium ions) given slowly over a period of 5-15 minutes is followed by an infusion of 1 g (5 mL of a 20% w/v solution equivalent to 4 mmol of magnesium ions) per hour for 24 hours after the last seizure.

Prevention and control of recurrent seizures in eclampsia:

An intravenous loading dose of typically 4 g (20 mL of a 20% w/v solution equivalent to 16 mmol of magnesium ions) given slowly over a period of 5-15 minutes is followed by an infusion of 1 g (5 mL of a 20% w/v solution equivalent to 4 mmol of magnesium ions) per hour continued for 24 hours after the last seizure or delivery postpartum (whichever is later).

If seizures recur, a further 2-4 g (10-20 mL of a 20% w/v solution equivalent to 8-16 mmol of magnesium ions), depending on the woman's weight, 2 g (8 mmol) if less than 70 kg, is given intravenously over 5 minutes. 4). Caution must be observed to prevent exceeding the renal capacity.

Summary of Safety Profile Commonly reported adverse reactions include flushing, nausea and vomiting, thirst, muscle weakness. The most important serious adverse reactions associated with magnesium sulfate relate to hypermagnesaemia.

These include respiratory depression leading to cardiac arrest. Tabulated Summary of Adverse Reactions Adverse reactions associated with intravenous magnesium sulfate from clinical studies and case reports are tabulated below. The table is presented in order of system organ class.

System Organ Class Adverse reaction Immune system disorders Hypersensitivity reactions Metabolic and nutritional disorders Hypophosphataemia, hyperosmolar dehydration, hypocalcaemia, hypermagnesaemia, hypoglycaemia Nervous system disorders Headache, dizziness, slurred speech, drowsiness and confusion, coma Eye disorders Visual disturbances including diplopia ptosis or abnormal vision Cardiac disorders ECG changes (prolonged PR, QRS and QT intervals), bradycardia, tachycardia, cardiac arrythmias, cardiac arrest Vascular disorders Flushing, peripheral vasodilation leading to hypotension Respiratory, thoracic and mediastinal disorders Dyspnoea, pulmonary oedema, respiratory depression, respiratory arrest Gastrointestinal disorders Nausea, vomiting, thirst Skin and subcutaneous tissue disorders Urticaria Musculoskeletal and connective tissue disorders Loss of tendon reflexes due to neuromuscular blockade, muscle weakness General disorders and administration site conditions Pain, burning, inflammation and bruising at injection site There have been isolated reports of maternal and foetal hypocalcaemia with high doses of magnesium sulfate.

Especially in patients with impaired renal function, there may be sufficient accumulation of magnesium sulfate to produce toxic effects. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important.

Concentrations of more than 5% w/v magnesium sulfate have a high osmolarity and may cause venous irritation and tissue damage in cases of extravasation, monitor the insertion site closely. 2). Due to the risk of respiratory depression as a result of hypermagnesaemia, patients should be closely monitored for signs and symptoms of magnesium toxicity.

In particular, caution is required in patients with respiratory disease. Parenteral magnesium should be used with caution in individuals with myasthenia gravis, to prevent an exacerbation of the condition or the precipitation of a myasthenic crisis.

A risk-benefit assessment should be performed in the individual cases prior to initiation of treatment. Serum calcium levels should be routinely monitored in patients receiving magnesium sulfate. Maternal administration of magnesium sulfate for longer than 5–7 days in pregnancy has been associated with skeletal adverse effects and hypocalcaemia and hypermagnesaemia in neonates.

If use of magnesium sulfate in pregnancy is prolonged or repeated, consider monitoring of neonates for abnormal calcium and magnesium levels and skeletal adverse effects.

1. Severe renal failure. Hepatic encephalopathy, hepatic failure. Parenteral magnesium salts should generally be avoided in patients with a heart block.