magnesium sulfate

Magnesium sulfate is a salt of magnesium, an important mineral for normal body functioning, including nerves and muscles. It is used to prevent and treat seizures caused by preeclampsia and eclampsia in pregnant women with high blood pressure and organ damage. It is also used to treat heart rhythm disorders, magnesium deficiency, and kidney inflammation in children. This medication works by depressing the central nervous system, reducing the release of a chemical that makes muscles contract, lowering heart rate, and improving kidney function.

Conditions treated with magnesium sulfate:

Adult

• Hypomagnesemia (low magnesium levels)
• Preeclampsia and eclampsia (toxemia of pregnancy)
• Torsades de pointes (heart rhythm disorder)
• Preterm labor (off-label use)

Pediatric

• Acute nephritis
• Hypomagnesemia
• Bronchospasm (off-label use)

Warnings

• Avoid magnesium sulfate if:
• You have hypersensitivity to the medication
• You have myocardial damage or heart block
• You are in a diabetic coma
• You have high magnesium levels
• You have high calcium levels

Side effects

Side effects of magnesium sulfate may include flushing, increased sweating, low blood pressure, depressed reflexes, flaccid paralysis, low core body temperature, circulatory collapse, depressed cardiac function, CNS depression, respiratory paralysis, excess fluid in the lungs, extreme drowsiness, visual changes, headache, breathing difficulties, muscle tightness, weakness, feeling faint, cold feeling, confusion, and anxiety.

Dosages

Injectable solution

Infusion solution

Adult

Hypomagnesemia

• Mild: 1 g intramuscularly (IM) every 6 hours for 4 doses
• Severe: 5 g intravenously (IV) over 3 hours
• Maintenance: 30-60 mg/kg/day IV

Toxemia of Pregnancy

• IV: 4-5 g diluted in 250 mL normal saline or D5W, in combination with either (a) up to 10 g (10 mL of undiluted 50% solution) administered intramuscularly (IM) into each buttock or (b) after initial IV dose, 1-3 g/hour IV

Torsades de Pointes

• With pulse (ACLS): 1-2 g slow IV diluted in 50-100 mL D5W over 5-60 minutes, followed by 0.5-1 g/hour IV
• Cardiac arrest (ACLS): 1-2 g slow IV diluted in 10 mL D5W over 5-20 minutes

Preterm Labor (Off-label)

Used as a labor suppressant (tocolytic) to stop preterm labor

• Loading dose: 4-6 g IV over 20 minutes; maintenance: 2-4 g/hour IV for 12-24 hours
• Do not exceed 5-7 days of continuous treatment; longer treatment duration may lead to low blood calcium in developing fetuses resulting in skeletal abnormalities

Dosing Modifications

• Severe renal impairment: Do not exceed 20 g/48 hours

Pediatric

Acute Nephritis

• IM: 100 mg/kg every 4-6 hours as needed or 20-40 mg/kg as needed
• IV: 100-200 mg/kg as 1-3% solution; total dose administered within 1 hour, with half given in the first 15-20 minutes

Hypomagnesemia

• IV/IM: 25-50 mg/kg every 4-6 hours for 3-4 doses as needed
• Oral: 100-200 mg/kg every 6 hours

Bronchospasm (Off-label)

• IV: 25-50 mg/kg over 10-20 minutes

Overdose

• Symptoms of magnesium overdose include a sharp drop in blood pressure and respiratory paralysis
• Onset of magnesium intoxication may be detected by the disappearance of kneecap (patellar) reflex
• Treatment of magnesium overdose often requires artificial ventilation, and intravenous calcium is used to counteract the effects of excess magnesium
• Hypermagnesemia in newborns may require resuscitation, assisted ventilation, and intravenous calcium

Drug interactions

Inform your doctor of all medications you are currently taking to avoid possible drug interactions. Magnesium sulfate has no known severe interactions with other drugs. Serious interactions include demeclocycline, doxycycline, eltrombopag, lymecycline, minocycline, oxytetracycline, and tetracycline.

Always tell your doctor, pharmacist, or healthcare provider about all prescription and over-the-counter medications you are using and their dosages. Keep a complete list and consult your doctor if you have any questions about your medication.

Pregnancy and breastfeeding

• Use magnesium sulfate during pregnancy only in life-threatening emergencies when no safer drug is available.
• Magnesium sulfate can cause fetal abnormalities when used for longer than 5-7 days in pregnant women.
• Continuous long-term use of magnesium sulfate in pregnant women for preterm labor treatment may result in skeletal abnormalities in newborns.
• Magnesium sulfate administered by continuous IV infusion in toxemic women may cause magnesium toxicity in the newborn.
• The safety and efficacy of magnesium sulfate for delaying preterm labor are not established.
• Caution should be exercised when using magnesium sulfate in nursing mothers.

Summary

Magnesium sulfate is a salt of magnesium, used to prevent and treat seizures from preeclampsia and eclampsia in pregnant women. It is also used to treat heart rhythm disorders, magnesium deficiency, and kidney inflammation in children. Common side effects include flushing, increased sweating, low blood pressure, depressed reflexes, paralysis, low body temperature, circulatory collapse, depressed heart function, CNS depression, respiratory paralysis, excess fluid in the lungs, drowsiness, and others.