magnesium oxide

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 (Mg) [mag-ne´ze-um]
a chemical element, atomic number 12, atomic weight 24.312. (See Appendix 6.) Its salts are essential in nutrition, being required for the activity of many enzymes, especially those concerned with oxidative phosphorylation. It is found in the intra- and extracellular fluids and is excreted in urine and feces. The normal serum level is approximately 2 mEq/L. Magnesium deficiency causes irritability of the nervous system with tetany, vasodilation, convulsions, tremors, depression, and psychotic behavior.
Homeostasis of magnesium in extracellular fluids. The normal serum magnesium level is regulated by intestinal and renal function. Most of the body's magnesium is stored in bones, muscle, and soft tissue. From Malarkey and McMorrow, 2000.
magnesium carbonate an antacid.
magnesium chloride an electrolyte replenisher and a pharmaceutic necessity for hemodialysis and peritoneal dialysis fluids.
magnesium citrate a saline laxative used for bowel evacuation before diagnostic procedures or surgery of the colon; administered orally.
magnesium hydroxide an antacid and cathartic.
magnesium oxide an antacid and a sorbent in pharmaceutical preparations; called also magnesia.
magnesium salicylate see salicylate.
magnesium silicate MgSiO3, a silicate salt of magnesium; the most common hydrated forms found in nature are asbestos and talc.
magnesium sulfate Epsom salt; an anticonvulsant and electrolyte replenisher, also used as a laxative and local antiinflammatory.
magnesium trisilicate a combination of magnesium oxide and silicon dioxide with varying proportions of water; used as a gastric antacid.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

magnesium chloride

magnesium citrate

Citramag (UK), Citro-Mag (CA), Citroma

magnesium gluconate

Mag G, Magonate

magnesium hydroxide

Dulcolax Milk of Magnesia, Phillips Milk of Magnesia, Phillips Milk of Magnesia Concentrate

magnesium oxide

Mag-ox, Uro-Mag

magnesium sulfate

Epsom Salts

Pharmacologic class: Mineral

Therapeutic class: Electrolyte replacement, laxative, antacid, anticonvulsant

Pregnancy risk category A (magnesium sulfate), NR (magnesium citrate, hydroxide, oxide), unknown (magnesium chloride, gluconate)


Increases osmotic gradient in small intestine, which draws water into intestines and causes distention. These effects stimulate peristalsis and bowel evacuation. In antacid action, reacts with hydrochloric acid in stomach to form water and increase gastric pH. In anticonvulsant action, depresses CNS and blocks transmission of peripheral neuromuscular impulses.


magnesium chloride

Injection: 20%

magnesium citrate

Oral solution: 240-ml, 296-ml, and 300-ml bottles

magnesium gluconate

Liquid: 1,000 mg/5 ml

Tablets: 500 mg

magnesium hydroxide

Liquid: 400 mg/5 ml

Liquid concentrate: 800 mg/5 ml

Tablets (chewable): 300 mg

magnesium oxide

Capsules: 140 mg

Tablets: 250 mg, 400 mg, 420 mg, 500 mg

magnesium sulfate

Granules (for oral use): 120 g, 4 lb

Injection: 10%, 12.5%, 25%, 50%

Indications and dosages

Mild magnesium deficiency

Adults: 1 g (2 ml of 50% sulfate solution) I.M. q 6 hours for four doses

Severe hypomagnesemia

Adults: 250 mg (2 mEq)/kg (sulfate) I.M. within 4-hour period, or 5 g (approximately 40 mEq) in 1 liter 5% dextrose injection or 0.9% sodium chloride solution by I.V. infusion over 3 hours

Hypomagnesemia treatment

Adults and children: Dosage individualized based on severity of deficiency; may give citrate, gluconate, hydroxide, oxide, or sulfate.

Hypomagnesemia prophylaxis

Adults and children: Dosage based on normal recommended daily magnesium intake; may give citrate, gluconate, hydroxide, oxide, or sulfate.

Supplemental magnesium in total parenteral nutrition (TPN)

Adults: 8 to 24 mEq/day (sulfate) by I.V. infusion, added to TPN solution


Adults and children ages 12 and older: 15 g (sulfate granules) in 240 ml water; or 30 to 60 ml/day P.O. (hydroxide) given with water; or a single dose of 10 to 30 ml P.O. (hydroxide concentrate); or one bottle of oral solution (citrate), as directed

Children ages 6 to 11: 5 to 10 g (sulfate granules) in 120 ml water; or a single dose of 2.5 to 5 ml P.O. (sulfate) in a half-glass of water; or 15 to 30 ml P.O. daily (hydroxide) given with water; or a single dose of 7.5 to 15 ml P.O. (hydroxide concentrate); or three to four tablets (hydroxide); or 50 to 100 ml, as directed, of oral solution (citrate)

Children ages 2 to 5: Single dose of 5 to 15 ml P.O. (hydroxide); or 2.5 to 7.5 ml P.O. daily (hydroxide concentrate); or one to two tablets (hydroxide); or 4 to 12 ml oral solution (citrate), as directed


Adults and children ages 12 and older: 5 to 15 ml P.O. (hydroxide liquid) up to q.i.d. with water; or 2.5 to 7.5 ml P.O. (hydroxide liquid concentrate) up to q.i.d. with water; or 622 to 1,244 mg P.O. (hydroxide tablets) up to q.i.d.; or 400 to 800 mg P.O. (oxide tablets) daily

To prevent and control seizures in preeclampsia or eclampsia

Adults: 4 to 5 g 50% sulfate solution I.M. q 4 hours, as necessary; or 4 g 10% to 20% sulfate solution I.V., not to exceed 1.5 ml/minute of 10% solution; or 4 to 5 g I.V. infusion in 250 ml of 5% dextrose or sodium chloride solution, not to exceed 3 ml/minute

Acute nephritis to control hypertension, encephalopathy, and seizures in children

Children: 100 mg/kg 50% sulfate solution I.M. q 4 to 6 hours as needed; or 20 to 40 mg/kg 20% solution I.M., repeated as necessary

Off-label uses

• Bronchodilation in some asthmatic patients

• Post-myocardial infarction hypomagnesemia


• Hypermagnesemia

• Heart block

• Myocardial damage

• Active labor or within 2 hours of delivery


Use cautiously in:

• renal insufficiency, abdominal pain, nausea and vomiting, rectal bleeding, anuria, hypocalcemia

• pregnant patients.


Be aware that magnesium sulfate injection is a high-alert drug.

• Know that I.V. use is reserved for life-threatening seizures.

• When giving magnesium sulfate I.V., don't exceed concentration of 20% or infusion rate of 150 mg/minute, except in seizures caused by severe eclampsia. Too-rapid I.V. infusion may cause hypotension and asystole.

• When giving magnesium sulfate I.M. to adults, use concentration of 25% to 50%; when giving to infants and children, don't exceed 20%.

Adverse reactions

CNS (with I.V. use): confusion, decreased reflexes, dizziness, syncope, sedation, hypothermia, paralysis

CV (with I.V. use): hypotension, arrhythmias, circulatory collapse

GI: nausea, vomiting, cramps, flatulence, anorexia

Metabolic: hypermagnesemia, hypocalcemia

Musculoskeletal (with I.V. use): muscle weakness, flaccidity

Respiratory: respiratory paralysis Skin: diaphoresis

Other: allergic reaction, injection site reaction, laxative dependence (with repeated or prolonged use)


Drug-drug. Aminoquinolones, nitrofurantoin, penicillamine, tetracyclines: decreased absorption of these drugs (with oral magnesium)

CNS depressants: additive effects

Digoxin: heart block, conduction changes (with I.V. use)

Enteric-coated drugs: faster dissolution of these drugs

Neuromuscular blockers: increased effects of these drugs (with I.V. use)

Drug-diagnostic tests. Calcium, magnesium: increased levels (with I.V. use)

Patient monitoring

When giving prolonged or repeated I.V. infusions, assess patellar reflex and monitor for respiratory rate of 16 breaths/minute or more.

With I.V. use, monitor blood magnesium level (desired level is 3 to 6 mg/dl or 2.5 to 5 mEq/L). Check for signs and symptoms of magnesium toxicity (hypotension, nausea, vomiting, ECG changes, muscle weakness, mental or respiratory depression, coma). Keep injectable calcium on hand to counteract magnesium toxicity.

• Monitor urine output, which should measure 100 ml or more every 4 hours.

If I.V. magnesium was given before delivery, assess neonate for signs and symptoms of magnesium toxicity, such as neuromuscular or respiratory depression.

• Monitor electrolyte levels and liver function tests.

Patient teaching

Teach patient about adverse reactions. Instruct him to report symptoms that occur during I.V. administration.

• Advise patient to consult prescriber before using magnesium if he's taking other drugs. Magnesium may delay or enhance absorption of other drugs.

• Inform patient that repeated or prolonged use of magnesium citrate, hydroxide, or sulfate may cause laxative dependence. Inform him that healthy diet and exercise can reduce need for laxatives.

• Tell pregnant female to make sure prescriber knows she is pregnant before taking drug.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved

mag·ne·si·um ox·ide

an antacid and laxative.
Farlex Partner Medical Dictionary © Farlex 2012

mag·ne·si·um ox·ide

(mag-nēzē-ŭm oksīd)
An antacid and laxative.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

magnesium oxide

An antacid drug. Brand name of preparations containing magnesium oxide and DIMETHICONE (dimeticone) are Asilone and Kolanticon.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005