Magnesium Sulfate use while Breastfeeding
Drugs containing Magnesium Sulfate: Suprep, Epsom Salt, Suprep Bowel Prep Kit, Sulfamag
Magnesium Sulfate Levels and Effects while Breastfeeding
Summary of Use during Lactation
Although intravenous magnesium sulfate given prior to delivery might affect the infant's ability to breastfeed, intention to breastfeed may be a more important determinant of breastfeeding initiation. Intravenous magnesium increases milk magnesium concentrations only slightly and oral absorption of magnesium by the infant is poor, so maternal magnesium therapy is not expected to affect the breastfed infant's serum magnesium. Magnesium sulfate can be taken during breastfeeding and no special precautions are required.
Maternal Levels. Ten women with pre-eclampsia were given 4 grams of magnesium sulfate intravenously followed by 1 gram per hour until 24 hours after delivery. While the average serum magnesium was 35.5 mg/L in treated women compared to 18.2 mg/L in 5 untreated controls, colostrum magnesium levels at the time of discontinuation of the infusion was 64 mg/L in treated women and 48 mg/L in the controls. By 48 hours after discontinuation, colostrum magnesium levels were only slightly above control values and by 72 hours they were virtually identical to controls.
Infant Levels. Relevant published information was not found as of the revision date.
Effects in Breastfed Infants
Fifty mothers who were in the first day postpartum received 15 mL of either mineral oil or an emulsion of mineral oil and another magnesium salt, magnesium hydroxide equivalent to 900 mg of magnesium hydroxide, although the exact number who received each product was not stated. Additional doses were given on subsequent days if needed. None of the breastfed infants were noted to have any markedly abnormal stools, but all of the infants also received supplemental feedings.
Effects on Lactation and Breastmilk
One mother who received intravenous magnesium sulfate for 3 days for pregnancy-induced hypertension had lactogenesis II delayed until day 10 postpartum. No other specific cause was found for the delay, although a complete work-up was not done. A subsequent controlled clinical trial found no evidence of delayed lactation in mothers who received intravenous magnesium sulfate therapy. Some, but not all, studies have found a trend toward increased time to the first feeding or decreased sucking in infants of mothers treated with intravenous magnesium sulfate during labor because of placental transfer of magnesium to the fetus. Another study found that among women with severe pre-eclampsia who received intravenous magnesium sulfate for up to one day postpartum and who intended to breastfeed, 85% of infants receiving routine well-baby care and 69% of those admitted to the NICU, breastfeeding was successfully initiated.
Alternate Drugs to Consider
1. Cordero L, Valentine CJ, Samuels P et al. Breastfeeding in women with severe preeclampsia. Breastfeed Med. 2012;7:457-63. PMID: 22871169
2. Cruikshank DP , Varner MW, Pitkin RM. Breast milk magnesium and calcium concentrations following magnesium sulfate treatment. Am J Obstet Gynecol. 1982;143:685-8. PMID: 7091241
3. Baldwin WF. Clinical study of senna administration to nursing mothers.:assessment of effects on infant bowel habits. Can Med Assoc J. 1963;89:566-7. PMID: 14045350
4. Haldeman W. Can magnesium sulfate therapy impact lactogenesis? J Hum Lact. 1993;9:249-52. PMID: 8260059
5. Riaz M, Porat R et al. The effects of maternal magnesium sulfate treatment on newborns: a prospective controlled study. J Perinatol. 1998;18:449-54. PMID: 9848759
6. Rasch DK, Huber PA et al. Neurobehavioral effects of neonatal hypermagnesemia. J Pediatr. 1982;100:272-6. PMID: 7199083
Magnesium Sulfate Identification
CAS Registry Number
LactMed Record Number
Last Revision Date
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