 Magnesium sulfate heptahydrate | |
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| Trade names | Epsom salt, others |
| AHFS/Drugs.com | Monograph |
| Routes of administration | IV, IM, by mouth, topical |
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| Chemical and physical data | |
| Formula | MgSO4 – 7H2O |
| Molar mass | 246.47 (Magnesium Sulfate Heptahydrate) |
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Magnesium sulfate as a medication is used to treat and preventlow blood magnesium and seizures in women witheclampsia.[1] It is also used in the treatment oftorsades de pointes, severeasthma exacerbations,constipation, andbarium poisoning.[1][2] It is given byinjection into a vein ormuscle as well as by mouth.[1][2] AsEpsom salt, it is also used formineral baths.[3]
Common side effects includelow blood pressure,skin flushing, andlow blood calcium.[1] Other side effects may include vomiting, muscle weakness, and decreased breathing.[4] While there is evidence that use duringpregnancy may harm the baby, the benefits in certain conditions are greater than the risks.[5] Its use duringbreastfeeding is deemed to be safe.[5] The way it works is not fully understood, but is believed to involve depressing the action ofneurons.[1]
Magnesium sulfate came into medical use at least as early as 1618.[6] It is on theWorld Health Organization's List of Essential Medicines.[7][8] In 2021, magnesium salts were the 211th most commonly prescribed medication, with more than 2 million prescriptions.[9][10]
Magnesium sulfate is available as magnesium sulfate dihydrate,[11] magnesium sulfate heptahydrate,[2][12] and magnesium sulfate monohydrate.[13]
The World Health Organization recommends magnesium sulfate heptahydrate for medical injection.[14]
Magnesium sulfate is used inbath salts, especially for foot baths to soothe sore feet. The reason for the inclusion of the salt is partially cosmetic: the increase in ionic strength prevents some of the temporary skin wrinkling (partial maceration) which would occur with plain water baths.
Epsom salt baths have been claimed to also soothe and hasten recovery of muscle pain, soreness, or injury. However, these claims have not been scientifically confirmed.[15] The solubility of magnesium sulfate water is inhibited by lipids in lotions resulting in variable absorption rates when applied to the skin. Temperature and concentration are also factors.[16]
Research ontopical magnesium (for example Epsom salt baths) is limited.[17]
Magnesium sulfate is commonly used inflotation therapy to prepare the concentrated solutions that fill theisolation tanks. Its high solubility in water yields baths with highspecific gravity that make the body more buoyant. Its negligible toxicity is an important asset in that application.
Magnesium and sulfate ions are naturally present in somemineral waters.[18]
In the United Kingdom, a medication containing magnesium sulfate, called "drawing paste", is claimed to be useful for smallboils or localisedinfections,[19] and removing splinters.[20] The standardBritish Pharmacopoeia composition is dried magnesium sulfate 47.76% (by mass),phenol 0.49%, andglycerol to balance.[19]
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Magnesium sulfate can be administered internally by oral, respiratory,intravenous, or intrathecal routes.
Injected magnesium sulfate is used as a replacement therapy formagnesium deficiency.[21]
Orally administered magnesium sulfate islaxative and thus the magnesium is not well absorbed.
Magnesium sulfate may be used as anantiarrhythmic agent fortorsades de pointes incardiac arrest under the ECC guidelines and for managingquinidine-induced arrhythmias.[22]
Magnesium sulfate may be used asbronchodilator afterbeta-agonist andanticholinergic agents have been tried, e.g. in severe exacerbations ofasthma,[23] The salt can be administered bynebulization[23] or byintravenous injection.
Magnesium sulfate is effective in decreasing the risk thatpre-eclampsia progresses toeclampsia.[24] Intravenous magnesium sulfate is used to prevent and treat seizures of eclampsia. It reduces thesystolic blood pressure but does not alter thediastolic blood pressure, so the blood perfusion to the fetus is not compromised. It is also commonly used for eclampsia where compared todiazepam orphenytoin it results in better outcomes.[25][26]
Magnesium sulfate was once used as atocolytic,[27][28] but meta-analyses have failed to support it as an anti-contraction medication.[29][30] Usage for prolonged periods (more than five to seven days) may result in health problems for the baby.[31]
In those at risk of an early delivery (preterm birth), treatment with magnesium sulfate has a neuroprotective role and decreases the risk ofcerebral palsy.[32][33] TheWorld Health Organization strongly recommends use of magnesium sulfate for women with risk of imminent birth before 32 weeks of gestation.[34] It is unclear if it helps those who are born at term.[32] Guidelines for the use of magnesium sulfate in mothers at risk of preterm labour are not strongly adhered to[35] and the effects of this treatment later in early childhood are unknown.[32][36][37]
Magnesium sulfate is used to treatbarium chloride poisoning,[38] where sulfate binds to barium to form insolublebarium sulfate.
Magnesium sulfate was historically used as a treatment forlead poisoning. Prior to the development ofchelation therapy, cases of accidental lead ingestion were often immediately treated with magnesium sulfate, which would cause the lead to be precipitated out and, with a high enough dose, literally purged from the digestive system as insolublelead(II) sulfate.[39][40] In this application, magnesium sulfate saw particular use in veterinary medicine of the early-to-mid 20th century; Epsom salt was already available on many farms for agricultural purposes, and it was often prescribed in the treatment of farm animals which inadvertently ingested lead.[41][42]
Magnesium sulfate can be administered intrathecally with opioids to prolong their analgesic duration.[43]
Magnesium sulfate has been used as an experimental treatment ofIrukandji syndrome caused by envenomation by certain species ofIrukandji jellyfish, but the efficacy of this treatment remains unproven.[44]
An abnormally elevated plasma concentration of magnesium is calledhypermagnesemia.
Previous ACLS guidelines addressed the use of magnesium in cardiac arrest with polymorphic ventricular tachycardia (ie, torsades de pointes) or suspected hypomagnesemia, and this has not been reevaluated in the 2015 Guidelines Update. These previous guidelines recommended defibrillation for termination of polymorphic VT (ie, torsades de pointes), followed by consideration of intravenous magnesium sulfate when secondary to a long QT interval.
The treatment of acute lead-poisoning consists in the evacuation of the stomach, if necessary, the exhibition of the sulphate of sodium or of magnesium, and the meeting of the indications as they arrive. The Epsom and Glauber's salts act as chemical antidotes, by precipitating the insoluble sulphate of lead, and also, if in excess, empty the bowel of the compound formed.
Udall (1) suggests sodium citrate as of some value together with Epsom salts which will bring about a precipitation of the lead in the form of an insoluble compound. Nelson (3) reported a case that survived following the use of a 20% magnesium sulphate solution intravenously, subcutaneously and orally. McIntosh (5) has suggested that purgative doses of Epsom salts may be effective in combining with the lead and overcoming the toxicity.
The specific antidotes to metal poisoning had not been discovered and the only thing which sometimes did a bit of good was magnesium sulphate which caused the precipitation of insoluble lead sulphate. The homely term for magnesium sulphate is, of course, epsom salts.
