Magnesium is an important cofactor of enzymatic reactions and plays an important role in neurochemical transmission and muscle excitability.

Magnesium prevents or controls convulsions by blocking neuromuscular transmission and decreasing the amount of acetyl choline librated at the end plate by the motor nerve impulse.

Magnesium cause depression by affecting central nervous system.

With intravenous administration the onset of anticonvulsant action is immediate and lasts about 30 minutes. Following intramuscular administration the onset of action occurs in about one hour and persists for three to four hours.

Magnesium is excreted by the kidney.

Normal magnesium serum levels range between 1.3-2 mEq/L.

 

Convulsions (treatment) - Intravenous magnesium sulfate is indicated for immediate control of lifethreatening convulsions in the treatment of severe toxemias (pre-eclampsia and eclampsia) of pregnancy and in the treatment of acute nephritis in children.

Hypomagnesemia (prophylaxis and treatment) - Magnesium Sulfate is indicated for replacement therapy in magnesium deficiency, especially in acute hypomagnesemia accompanied by signs of tetany similar to those of hypocalcemia.

Magnesium Sulfate is also used to prevent or treat magnesium deficiency in patients receiving total parenteral nutrition.

Tetany, uterine (treatment) - Magnesium Sulfate is indicated in uterine tetany as a myometrial relaxant.

 

Intramuscular therapy in adults: For severe hypomagnesaemia 1 to 5 g (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 g (2ml of 50% solution) can be given once or twice daily. Serum magnesium should serve as a guide to continued dosage.

Intravenous: 1 to 4 g magnesium sulfate may be given intravenously in 10% to 20% solution, but only with great caution, the rate should not exceed 1.5ml of 10% solution or equivalent per minute until relaxation is obtained. Intravenous infusion: 4 g in 250ml of 5% Dextrose injection at a rate not exceeding 3 ml per minute.

Usual dose range: 1 to 40 g per day.

Electrolyte replenisher: Intramuscular 1 to 2 g 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 g in 25% solution is given intramuscularly. Subsequently, 1 g is given every 30 minutes until relief is obtained. The blood

pressure should be monitored after each injection.

 

Magnesium sulfate should not be administered parenterally in patients with heart block or myocardial damage.

Intravenous magnesium should not be given to mothers with toxemia of pregnancy during the tow hours preceding delivery.

 

- Because magnesium is removed from the body solely by kidney, the drug should be used with caution in patients with renal impairment. Monitoring serum magnesium levels and patient's clinical status is essential to avoid the consequence of overdose in toxaemia.

- Clinical indications of a safe dosage regimen include the presence of patellar reflex (knee jerk) and absence of respiratory depression.  

- Serum magnesium levels usually sufficient to control convulsions range from 3 to 6 mg/100ml (2.5 to 5 mEq/l). The strength of the deep tendon reflexes begin to diminish when serum magnesium levels exceed 4 mEq/L.  Reflex may be absent at 10mEq magnesium/L, where respiratory paralysis is a potential hazard.

- An injectable calcium salt should be immediately available to counteract the potential hazards of magnesium intoxication in eclampsia.

 

Flushing, sweating, sharply lowered blood pressure, hypothermia, stupor and ultimately respiratory depression.

The adverse effects of parenterally administered magnesium usually are the result of magnesium intoxication. These include flushing, sweating, hypotension, depressed reflexes, flaccid paralysis, hypothermia, circulatory collapse, cardiac and central nervous system depression proceeding to respiratory paralysis.

Hypocalcemia with signs of tetany secondary to magnesium sulfate therapy for eclampsia has been reported.

 

Magnesium Sulfate 50% for injection : 10mlor 2ml of sterile injection solution in plastic ampoule contains: Magnesium Sulfate 50g/100ml which equivalent to 2.00 mMol/ml ofMg+2.

 

Store between (15-30)°C and protect from light.