Magnesium Oxide use while Breastfeeding
Drugs containing Magnesium Oxide: Prepopik, Mag-Ox, Mag-Oxide, Clenpiq, Mag-Ox 400, Mag-200, Uro-Mag, MagGel, Phillips' Cramp-free, Mag-Caps
Medically reviewed on January 30, 2018
Magnesium Oxide Levels and Effects while Breastfeeding
Summary of Use during Lactation
No information is available on the clinical use of magnesium oxide during breastfeeding. However, other magnesium salts have been studied. A study on the use of magnesium hydroxide during breastfeeding found no adverse reactions in breastfed infants. Intravenous magnesium increases milk magnesium concentrations only slightly. Oral absorption of magnesium by the infant is poor, so maternal magnesium hydroxide is not expected to affect the breastfed infant's serum magnesium. Magnesium oxide supplementation during pregnancy might delay the onset of lactation, but it 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 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.
A study in 40 pairs of matched healthy women with vaginally delivered singleton pregnancies, outcome endpoints were compared in those receiving continuous oral magnesium aspartate HCl supplementation mean dose of 459 mg daily (range 365 to 729 mg of magnesium daily) for at least 4 weeks before delivery versus non-supplemented controls. In the magnesium group, significantly fewer women could breastfeed their infants exclusively at discharge (63% vs 80%).
Alternate Drugs to Consider
1. 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
2. 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
3. Haldeman W. Can magnesium sulfate therapy impact lactogenesis? J Hum Lact. 1993;9:249-52. PMID: 8260059
4. Riaz M, Porat R, Brodsky NL et al. The effects of maternal magnesium sulfate treatment on newborns: a prospective controlled study. J Perinatol. 1998;18:449-54. PMID: 9848759
5. Rasch DK, Huber PA, Richardson CJ et al. Neurobehavioral effects of neonatal hypermagnesemia. J Pediatr. 1982;100:272-6. PMID: 7199083
6. Meier B, Huch R, Zimmermann R et al. Does continuing oral magnesium supplementation until delivery affect labor and puerperium outcome? Eur J Obstet Gynecol Reprod Biol. 2005;123:157-61. PMID: 15899543
Magnesium Oxide Identification
CAS Registry Number
LactMed Record Number
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