What does magnesium sulfate do

Epsom saltDrug groupsSaltsLaxative Epsom salt is an active ingredient from the group of saline laxatives that is used for the short-term treatment of mild constipation. The substance is magnesium sulfate heptahydrate. Adults usually take 15 g dissolved in 250 ml water once a day. Possible adverse effects include digestive problems such as diarrhea, nausea, and abdominal cramps. Electrolyte disturbances can occur with long-term use. Epsom salts should not be administered at the same time as other medications and should not be overdosed.

Synonymous: Magnesium sulfate heptahydrate, Magnesii sulfas heptahydricusPhEur, Sal amarum, Epsom salt


Epsom salt is available as open goods in pharmacies and drugstores. The specialist trade can order it from specialized suppliers such as Hänseler. Epsom salt, as Epsom salt is also called, originally comes from Epsom, a suburb of London.

Structure and properties

Epsom salt is magnesium sulfate heptahydrate (MgSO4 · 7 H2O, Mr = 246.5 g / mol). It is available as a white, crystalline powder or as shiny, colorless crystals and is easily soluble in water. It dissolves even better in boiling water. The salt is odorless and has a salty-bitter taste. Epsom salt should be stored tightly closed and protected from light, heat and moisture.


Epsom salt (ATC A06AD04) has stool-softening and laxative properties. It osmotically retains water in the intestine, promotes water secretion into the intestine and thus increases the amount of fluid and the volume of the stool. The effects appear within about 6 hours.

application areas

For the short-term treatment of constipation. In alternative medicine for "purification" and when fasting.


Adults take 10 to 15 g of the powder dissolved in sufficient water once a day (e.g. 15 g in 250 ml of water). The taste can be improved by adding a little lemon juice.


Epsom salt is contraindicated for hypersensitivity, intestinal obstruction, inflammatory bowel disease, abdominal pain of unknown origin, kidney failure, electrolyte disorders and hypermagnesaemia. The complete precautionary measures can be found in the instructions for use.


Magnesium salts can impair the absorption of other drugs (e.g. tetracyclines, quinolones) and should therefore not be taken at the same time, but at least two to four hours apart. With hypokalaemia, the sensitivity to cardiac glycosides is increased.

unwanted effects

Possible adverse effects include digestive problems such as diarrhea, nausea, and abdominal cramps. Electrolyte disturbances can occur with long-term use. Abusive overdose can lead to dangerous magnesium poisoning.

see also

Sodium sulfate (Glauber's salt), laxative

  • Pharmaceutical patient information (CH, USA)
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  • European Pharmacopoeia PhEur
  • Hager's Handbook of Pharmaceutical Practice
  • Pharmacopoea Helvetica V
  • swell
  • Reynolds J. (Ed.) Martindale. The Extra Pharmacopoeia. London: The Pharmaceutical Press, 1989
  • Tofil N.M., Benner K.W., Winkler M.K. Fatal hypermagnesemia caused by an Epsom salt enema: a case illustration. South Med J, 2005, 98 (2), 253-6 Pubmed

Conflicts of Interest: None / Independent. The author has no relationships with the manufacturers and is not involved in the sale of the products mentioned.

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