Breast engorgement and galactorrhea during magnesium sulfate treatment of preterm labor.

Breast engorgement and galactorrhea occasionally occur during tocolysis with ritodrine. We are not aware of breast engorgement and galactorrhea associated with other tocolytics. We report the first case of breast engorgement and galactorrhea during tocolysis with intravenous magnesium sulfate in a generally healthy 24-year-old woman admitted for tocolysis at 30 weeks' gestation. Breast engorgement and galactorrhea gradually subsided after magnesium sulfate was discontinued. The rapid disappearance of both the galactorrhea and the breast engorgement after discontinuation of magnesium sulfate treatment suggests a cause-effect relationship, the mechanism of which remains unclear.