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Magnesium sulfate is most commonly used for the treatment
preeclampsia during pregnancy. Use of magnesium for
the treatment of
preterm labor or preeclampsia is an
unlabeled use of the medicine.
sulfate is sometimes used as a
tocolytic medicine to slow uterine contractions during
preterm labor. But studies show it does not stop preterm labor and it may cause
complications for both mother and baby.1
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, magnesium sulfate may be used to reduce the risk of
cerebral palsy in the premature newborn.2More research is needed to find out how well this works.3
Studies have shown that magnesium
sulfate is unlikely to stop preterm labor.4 It may
also cause complications for mother and baby.1
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)(What is a PDF document?) to help you understand this medication.
Grimes DA, Nanda K (2006). Magnesium sulfate
tocolysis: Time to quit. Obstetrics and Gynecology,
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):
American College of Obstetricians and Gynecologists (2010). Magnesium sulfate before anticipated preterm birth for neuroprotection. ACOG Committee Opinion No. 455. Obstetrics and Gynecology, 115(3): 669–671.
Haas DM (2010). Preterm birth, search date June 2009.
Online version of BMJ Clinical Evidence:
January 10, 2011
Sarah Marshall, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine
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