FDA Drug Safety Communication: FDA Recommends Against Prolonged Use of Magnesium Sulfate to Stop Pre-term Labor Due to Bone Changes in Exposed Babies

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Safety Announcement
[5-30-2013] The U.S. Food and Drug Administration (FDA) is advising health care professionals against using magnesium sulfate injection for more than 5-7 days to stop pre-term labor in pregnant women. This use of the drug is off-label, which means that it is not an FDA-approved use of the drug. Administration of magnesium sulfate injection to pregnant women longer than 5-7 days may lead to low calcium levels and bone problems in the developing baby or fetus, including thin bones, called osteopenia, and bone breaks, called fractures. The shortest duration of treatment that can result in harm to the baby is not known (see Data Summary).
Magnesium sulfate is approved to prevent seizures in preeclampsia, a condition in which the pregnant woman develops high blood pressure and protein in the urine, and for control of seizures in eclampsia. Both preeclampsia and eclampsia are life-threatening complications that can occur during pregnancy. Preeclampsia can lead to eclampsia, seizures, stroke, multiple organ failure, and death of the woman and/or baby.
In light of this new safety information about low calcium levels and bone problems in the developing baby, the following information is being added to the drug label for Magnesium Sulfate Injection, USP 50%:

A new Warning stating that continuous administration of magnesium sulfate injection beyond 5-7 days in pregnancy for the treatment of pre-term labor can cause low calcium levels and bone changes in the baby.
A new Teratogenic Effects section conveying the potential harm to developing babies by changing the Pregnancy Category to D from A. This section also includes the concerns described under the new Warning.

Pregnancy Category D means there is positive evidence of human fetal risk, but the potential benefits from using the drug in pregnant women may be acceptable in certain situations despite its risks.
Pregnancy Category A means that adequate and well-controlled studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy, and there is no evidence of risk in later trimesters.

A new Labor and Delivery section emphasizing that continuous administration of magnesium sulfate injection to treat pre-term labor is not approved and that the safety and efficacy of use for this indication are not established.

The manufacturers of other magnesium sulfate injection products have made similar changes to their drug labels.