Magnesium (pharmaceutical preparation)
Types of preparations 
Magnesium is practically always given in a salt form together with any of several anionic compounds serving as counter-ions, such as chloride or sulfate. Still, magnesium is generally presumed to be the active component. An exception is the administration of magnesium sulfate in barium chloride poisoning, where sulfate binds to barium to form insoluble barium sulfate.
Magnesium is absorbed orally at about 30% bioavailability from any water soluble salt, such as magnesium chloride or magnesium citrate. The citrate is the least expensive soluble (high bioavailability) oral magnesium salt available in supplements, with 100 mg and 200 mg magnesium typically contained per capsule or tablet.
Magnesium aspartate, chloride, lactate, citrate and glycinate each have bioavailability 4 times greater than the oxide form and are equivalent to each other per amount of magnesium, though not in price.
The ligand of choice for large-scale manufacturers of multivitamins and minerals containing magnesium is the magnesium oxide due to its compactness, high magnesium content by weight, low cost, and ease-of-use in manufacturing. However it is insoluble in water. Insoluble magnesium salts such as magnesium oxide or magnesium hydroxide (milk of magnesia) depend on stomach acid for neutralization before they can be absorbed, and thus are relatively poor oral magnesium sources, on average.
Magnesium sulfate (Epsom salts) are soluble in water, but are commonly used as a laxative, due to the poor absorption of the sulfate component. In lower doses, they may be used as an oral magnesium source, however.
Intravenous or intramuscular magnesium is generally in the form of magnesium sulfate solution. Intravenous or intramuscular magnesium is completely bioavailable, and effective. It is used in severe hypomagnesemia and eclampsia.
Indications and uses for administering magnesium include:
- Magnesium deficiency and hypomagnesemia.
- Eclampsia. Empirical and clinical evidence supports the effectiveness of magnesium for this use. For this purpose, magnesium may act as a vasodilator, with actions in the peripheral vasculature or the cerebrovasculature, to decrease peripheral vascular resistance or relieve vasoconstriction. Additionally, magnesium may also protect the blood–brain barrier and thereby limit formation of cerebral edema, or it may act as a central anticonvulsant. The preparation usually used for this purpose is magnesium sulfate.
- Laxative use, particularly magnesium citrate and magnesium hydroxide
- Antiarrhythmic agent for torsades de pointes in cardiac arrest. Magnesium sulfate is the first-line agent for such use under the 2005 ECC guidelines and for managing quinidine-induced arrhythmias.
- As a bronchodilator after beta-agonist and anticholinergic agents have been tried, e.g. in severe exacerbations of asthma. Recent studies have revealed that magnesium sulfate can be nebulized to reduce the symptoms of acute asthma. It is commonly administered via the intravenous route for the management of severe asthma attacks.
- Anti-contraction medication: Magnesium sulfate can also delay labor in the case of premature labor, to delay preterm birth.
Side effects 
More common side effects from magnesium include upset stomach and diarrhea, and calcium deficiency if calcium levels are already low.
Overdose of magnesium (hypermagnesemia) is only possible in special circumstances. It can cause nausea, vomiting, severely lowered blood pressure, confusion, slowed heart rate, respiratory paralysis. In very severe cases, it can cause coma, cardiac arrhythmia, cardiac arrest and death.
- Euser, A. G.; Cipolla, M. J. (2009). "Magnesium Sulfate for the Treatment of Eclampsia: A Brief Review". Stroke 40 (4): 1169–1175. doi:10.1161/STROKEAHA.108.527788. PMC 2663594. PMID 19211496.
- "BARIUM CHLORIDE DIHYDRATE 4. First Aid Measures". Jtbaker.com. Retrieved 2009-07-06.
- Firoz M, Graber M: "Bioavailability of US commercial magnesium preparations.", Magnesium Research 2001 Dec;14(4):257-62.
- Lindberg JS, Zobitz MM, Poindexter JR, Pak CY: "Magnesium bioavailability from magnesium citrate and magnesium oxide.",J Am Coll Nutr. 1990 Feb;9(1):48-55.
- "When clicking citation, it is listed under ''Other medicinal and home uses''". Disabled-world.com. 2007-01-04. Retrieved 2009-07-06.
- Blitz M, Blitz S, Hughes R, Diner B, Beasley R, Knopp J, Rowe BH. Aerosolized magnesium sulfate for acute asthma: a systematic review. Chest 2005;128:337-44. PMID 16002955.
- "Magnesium sulfate for preterm labor". Webmd.com. 2007-01-19. Retrieved 2009-07-06.
- Lewis DF (September 2005). "Magnesium sulfate: the first-line tocolytic". Obstet. Gynecol. Clin. North Am. 32 (3): 485–500. doi:10.1016/j.ogc.2005.03.002. PMID 16125045.
- Magnesium at University of Maryland Medical Center (UMMC). Reviewed last on: 6/17/2011 by Steven D. Ehrlich
- Omu AE, Al-Harmi J, Vedi HL, Mlechkova L, Sayed AF, Al-Ragum NS (2008). "Magnesium sulphate therapy in women with pre-eclampsia and eclampsia in Kuwait". Med Princ Pract 17 (3): 227–32. doi:10.1159/000117797. PMID 18408392.