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Magnesium sulfate is most commonly used for the treatment
preeclampsia during pregnancy. But magnesium
sulfate is sometimes used as a
tocolytic medicine to slow uterine contractions or to help protect the baby's brain during
Magnesium sulfate is usually given through a vein (intravenously) until contractions have slowed and the
cervix has stopped thinning (effacing) or opening
This medicine is thought to affect the
action of calcium in the body, and calcium must be present for the muscles of
the uterus to contract.
Magnesium sulfate may be used to
stop preterm labor when:
labor is likely to lead to preterm delivery and the mother is less than 32 weeks pregnant, magnesium sulfate may be used to reduce the risk of
certain problems with the baby's brain, such as cerebral palsy.1, 2
Studies have shown that magnesium
sulfate is unlikely to stop preterm labor.3 But if it's given to women in preterm labor who are less than 32 weeks pregnant, it may help reduce the risk of cerebral palsy in babies who are born preterm.4
Common side effects of this medicine include:
See Drug Reference for a full list of side effects. (Drug
Reference is not available in all systems.)
In rare cases, symptoms of magnesium toxicity (nausea, muscle weakness, loss of reflexes) occur during magnesium sulfate treatment. The medicine calcium gluconate is given to treat the problem.
Mothers on magnesium sulfate are closely monitored. Blood pressure and pulse are checked about every 30 minutes for at least the first few hours of treatment.
Complete the new medication information form (PDF)new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
American College of Obstetricians and Gynecologists (2012). Prediction and prevention of preterm birth. ACOG Practice Bulletin No. 130. Obstetrics and Gynecology, 120(4): 964–973.
Rouse DJ, et al. (2008). A randomized, controlled
trial of magnesium sulfate for the prevention of cerebral palsy.
New England Journal of Medicine, 359(9):
Haas DM (2011). Preterm birth, search date June 2010.
BMJ Clinical Evidence. Available online:
American College of Obstetricians and Gynecologists
(2012). Management of preterm labor. ACOG Practice Bulletin
No. 127. Obstetrics and Gynecology, 119(6):
January 8, 2013
Sarah Marshall, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine
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