Why is magnesium sulfate used in treating preterm labor?
When a woman experiences preterm labor (defined as contractions and cervical effacement or dilation before term), sometimes she is given magnesium sulfate, which is thought to relax the muscles of the uterus. It is not FDA approved for treating preterm labor and is used “off label” for this purpose. It was introduced in the United States as a preterm labor drug in 1969, on the basis of laboratory work. (Lancet, 1997, Vol. 350, p.
