Last update Aug. 31, 2020
Very Low Risk
Magnesium sulphate taken intravenously is used to treat certain arrythmias, eclampsia and convulsions of newborns and infants, orally as an osmotic laxative and in the prophylaxis of migraine (Pringsheim 2012) and, topically, for certain types of skin inflammation.
Daily magnesium requirements for breastfeeding mothers are estimated at 310 to 360 mg (MedlinePlus 2017); some countries have established figures of up to 450 mg daily (Hall 2010).
Since the last update we have not found any published data on its excretion in breast milk.
Magnesium is a natural component of milk. The average natural concentration of magnesium in milk is 31 mg/L (15 to 64 mg/L) (Dórea 2000, Feeley 1983).
Ingested magnesium is not concentrated in breastmilk. Its concentration in milk is very stable and depends little on diet (USD 2000) and other factors, including intravenous administration of magnesium sulphate to the mother: the levels of magnesium in milk of mothers treated with intravenous magnesium sulphate were 6.4 mg/L versus 4.8 mg/L in untreated patients (Cruikshank 1982, Dorea 2000), a clinically non-significant difference for the infant, which also disappeared within a few hours.
Its low oral bioavailability hinders transfer to plasma and, therefore, to breastmilk, as well as transfer to infant plasma via breastmilk (Morris 1987).
In women treated with magnesium sulphate before or during childbirth, there has been a delay in the stimulation of milk production or lactogenesis II (Haldeman 1993) and less frequency of breastfeeding (Meier 2005) as well as hypotonia in newborns (Riaz 1998, Rasch 1982), which could interfere with adequate breast stimulation, but this can be counteracted by a firm decision by the mother and effective support for her (Cordero 2012).
Various medical associations and expert consensus consider the use of various magnesium salts to be safe during breastfeeding (Hale 2019, Briggs 2015, Dennis 2012, Schaefer 2007, Mahadevan 2006, Richter 2005, Nice 2000, Broussard 1998, Idama 1998).
American Academy of Pediatrics: medication usually compatible with breastfeeding (AAP 2001).
List of WHO essential medicines: compatible with breastfeeding (WHO / UNICEF 2002).
If the intravenous administration of magnesium sulphate is considered compatible with breastfeeding, all the more reason that salts administered orally will also be compatible (Hagemann 1998).
We do not have alternatives for Magnesium Sulfate since it is relatively safe.
Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.
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e-lactancia is a resource recommended by Academy of Breastfeeding Medicine - 2012 of United States of America
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