magnesium sulfate (injection)

Magnesium sulfate injection is suitable for replacement therapy in magnesium deficiency, especially in acute hypomagnesemia accompanied by signs of tetany similar to those observed in hypocalcemia. Magnesium sulfate injection is also indicated for the prevention and control of seizures in pre-eclampsia and eclampsia, respectively.

Magnesium sulfate is a sterile solution of magnesium sulfate heptahydrate in water for injection. Magnesium sulfate prevents convulsions by blocking transmission between nerves and muscles. It also reduces the amount of t acetylcholine, a chemical that nerves use for communicating with other nerves and tissues.

Side effects of magnesium sulfate are:

• flushing,
• sweating,
• hypotension
• (low blood pressure),
• flaccid
• paralysis,
• lowered body temperature,
• cardiac and central nervous system depression.

Dosage of magnesium sulfate must be carefully adjusted according to individual requirements and response, and administration of the drug should be discontinued as soon as the desired effect is obtained.

Both IV and IM administration are appropriate. IM administration of the undiluted 50% solution results in therapeutic plasma levels in 60 minutes, whereas IV doses will provide a therapeutic level almost immediately. The rate of IV injection should generally not exceed 150 mg/minute (1.5 mL of a 10% concentration or its equivalent), except in severe eclampsia with seizures (see below). Continuous maternal administration of magnesium sulfate in pregnancy beyond 5 to 7 days can cause fetal abnormalities.

Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration. The diluents commonly used are 5% Dextrose Injection, USP and 0.9% Sodium Chloride Injection, USP. Deep IM injection of the undiluted (50%) solution is appropriate for adults, but the solution should be diluted to a 20% or less concentration prior to such injection in children.

Barbiturates, narcotics or other hypnotics or other drugs that slow brain function may add to the brain depressing effects of magnesium. Magnesium adds to the effect of neuromuscular blocking agents.

Magnesium sulfate should be administered with extreme caution in patients receiving digoxin (Lanoxin) due to the risk of abnormal heart beats.

Magnesium sulfate can cause fetal abnormalities, such as hypocalcemia, skeletal demineralization, osteopenia and other skeletal abnormalities, when administered beyond 5-7 days to pregnant women. It should be used only if clearly needed. If magnesium sulfate needs to be used during pregnancy, the woman should be informed of the potential risks to the newborn.

Magnesium sulfate enters breast milk therefore, it is best to be cautious before using it in nursing mothers.

What preparations of magnesium sulfate injection are available?

Intramuscular magnesium sulfate available in 500 mg/ml strength, in 2 ml, 10 ml, and 50 ml single-use vials.

Intravenous magnesium sulfate is available in 40mg/ml and 80mg/ml strengths. 40 mg/ml concentration is available in 50 ml, 100 ml, 500 ml, and 1000 ml single-dose, plastic containers. 80 mg/ml concentration is available in 50 ml partial-fill, single-dose, flexible plastic container.

How should I keep magnesium sulfate injection stored?

Intramuscular magnesium sulfate injections are stored between 15 C to 30 C (59 F to 86 F). Intravenous magnesium sulfate injections are stored between 20 C to 25 C (68 F to 77 F).