Magnesium Sulfate

Indications

Magnesium sulfate injection is indicated mainly for the treatment of acute hypomagnesemia and magnesium deficiency states. Magnesium sulfate also has anticonvulsant properties. It can be used for the prevention and control of seizures in pre-eclampsia and eclampsia, respectively.

Pharmacology

Magnesium is an important cofactor for enzymatic reactions. It plays an important role in neurochemical transmission and muscular excitability. Magnesium deficiency is accompanied by a variety of different structural and functional disturbances

Dosage & Administration

Intramuscular: Adults and older children: For severe hypomagnesemia, 1 to 5 gm (2 to 10 ml of 50% solution) daily in divided doses; administration is repeated daily until serum levels have returned to normal. If deficiency is not severe, 1 gm (2 ml of 50% solution) can be given once or twice daily. Serum magnesium levels should serve as a guide to continued dosage.

Intravenous: 1 to 4 gm magnesium sulfate (magnesium sulfate (magnesium sulfate injection) injection) may be given intravenously in 10% to 20% solution, but only with great caution; the rate should not exceed 1.5 ml of 10% solution or equivalent per minute until relaxation is obtained.

Usual Dose Range: 1 to 40 gm daily.

Electrolyte Replenisher: Intramuscular 1 to 2 gm in 50% solution four times a day until serum magnesium is within normal limits.

Usual Pediatric Dose: Intramuscular 20 to 40 mg per kg of body weight in a 20% solution repeated as necessary.

For Eclampsia: Initially 1 to 2 gm in 25% or 50% solution is given intramuscularly. Subsequently, 1 gm is given every 30 minutes until relief is obtained. The blood pressure should be monitored after each injection.

Interaction

The dosage of barbiturates, narcotics or other hypnotics (or systemic anesthetics), or other CNS depressants should be adjusted with caution when given in conjunction with magnesium due to the additive depressant effects of magnesium. There may be an increase in the effects of neuromuscular blocking agent when given together with magnesium sulfate. Magnesium sulfate may cause a reduction in blood pressure when administered together with calcium channel blockers.

Contraindications

Magnesium Sulfate contra-indicated in the case of defect of the heart's electrical message pathways resulting in decreased function of the heart (heart block), severe damage to the muscular wall of the heart (myocardium) and significantly decreased kidney function.

Side Effects

The most common side effect is hypermagnesaemia developing from excessive administration of magnesium. Symptoms of hypermagnesaemia may include nausea, vomiting, flushing of skin, thirst, hypotension due to peripheral vasodilatation, drowsiness, confusion, muscle weakness etc. Rarely diarrhea or skin irritation after soaking may occur.

Pregnancy & Lactation

Pregnancy: Magnesium sulfate injection should be used during pregnancy only if clearly needed. Magnesium sulfate is not known to be harmful for short-term intravenous administration in eclampsia but excessive doses cause neonatal respiratory depression. It is not known whether the drug is excreted in human milk. As it happens with many other drugs, cautions should be taken when it is administered to a nursing mother.

Precautions & Warnings

Magnesium salts should be administered with caution to patients with impaired renal function or those receiving digitalis glycosides. Parenteral administration of magnesium salts may enhance the effect of neuromuscular blocking agents or of central nervous system depressants. Monitor blood pressure, respiratory rate, urinary output and for signs of over dosage like loss of patellar reflex, weakness, nausea, sensation of warmth, flushing of skin, drowsiness, double vision and slurred speech.

Overdose Effects

Symptoms of magnesium intoxication are a sharp drop in blood pressure and respiratory paralysis. In the event of overdose, artificial ventilation must be provided until a calcium salt can be injected IV to antagonize the effects of magnesium.

Therapeutic Class

Specific mineral preparations

Storage Conditions

Store in a cool & dry place, keep away from light & children.