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Indications and Dosage
Intravenous
Hypomagnesaemia Adult: 4 g of Magnesium Chloride in 250 mL of 5% Dextrose inj given via IV infusion (Max rate: 3 mL/min). Monitor serum magnesium to guide subsequent dosage. Usual dosage range: 1-40 g Magnesium Chloride daily. Oral Dietary supplement Adult: Adjust according to individual requirement. RDA (elemental magnesium): 19-30 yr: Female: 310 mg/day, pregnant female: 350 mg/day, male: 400 mg/day. ≥31 yr: Female: 320 mg/day, pregnant female: 360 mg/day, male: 420 mg/day.
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Contraindications
Intravenous: Patients with renal impairment, marked myocardial disease, and comatose condition.
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Special Precautions
Risk of hypermagnesaemia in patients with renal impairment. Caution in myasthenia gravis, pregnancy. Oral: Take with food to reduce stomach upset and diarrhoea. Intravenous: Administer cautiously if sweating and flushing occurs. Monitor serum magnesium concentrations, respiratory rate, blood pressure, deep tendon reflex and renal function.
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Adverse Reactions
Oral: Watery diarrhoea, GI irritation. Intravenous: Nausea, vomiting, flushing, thirst, hypotension.
Potentially Fatal: Potentially Hazardous: Intravenous: Hypermagnesaemia may lead to respiratory depression, loss of deep tendon reflexes and cardiac arrest. |
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Overdosage
Symptoms of hypermagnesaemia: Respiratory depression and loss of deep tendon reflexes due to neuromuscular blockade; nausea, vomiting, flushing, hypotension, drowsiness, bradycardia and muscle weakness. Treatment: In patients with normal renal function, IV fluids or furosemide may be given to promote Magnesium excretion. In patients with symptomatic hypermagnesaemia, slow IV inj of calcium gluconate can be used to antagonise the cardiac and neuromuscular effects of Magnesium.
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Drug Interactions
Oral magnesium salts may decrease absorption of bisphosphonates, quinolone antibiotics and tetracycline derivatives; admin should be separated apart if concomitant use is required. Magnesium-containing products may reduce absorption of eltrombopag by 70%; separate admin by at least 4 hr. Calcitriol may increase serum concentrations of Magnesium salts. Magnesium salts may decrease serum concentrations of mycophenolate if used concurrently; monitor for reduced effects of mycophenolate. Concomitant use of trientine and magnesium salt may reduce serum concentrations of both agents.
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Action
Description: Magnesium is essential to many enzymatic reactions in the body, acting as a cofactor in protein synthesis and carbohydrate metabolism. 8.36 g of Magnesium chloride (hexahydrate) is equivalent to about 1 g of magnesium. Each g of magnesium chloride (hexahydrate) represents about 4.9 mmol of magnesium and 9.8 mmol of chloride.
Pharmacokinetics: Absorption: Oral: About one-third is absorbed from the small intestine. The fraction of magnesium absorbed is inversely proportional to amount ingested. Distribution: Plasma protein binding: About 25-30%. Magnesium crosses the placenta. Excretion: Parenteral magnesium salts: Excreted mainly in urine. Oral magnesium salts: Via urine (absorbed fraction); faeces (unabsorbed fraction). |
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Storage
Oral: Store at room temperature, away from light and moisture. Intravenous inj: Prior to reconstitution, store at 15-30°C (59-86°F).
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MIMS Class
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