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Magnesium Oxide

Pronunciation

Pronunciation

(mag NEE zhum OKS ide)

Index Terms

  • Mag Oxide

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral:

Uro-Mag: 140 mg

Tablet, Oral:

Mag-200: 200 mg [contains para-aminobenzoic acid]

Maox: 420 mg [contains tartrazine (fd&c yellow #5)]

Generic: 400 mg, 420 mg, 400 mg

Tablet, Oral [preservative free]:

Generic: 400 mg, 500 mg

Brand Names: U.S.

  • Mag-200 [OTC]
  • Maox [OTC]
  • Uro-Mag [OTC]

Pharmacologic Category

  • Electrolyte Supplement, Oral
  • Magnesium Salt

Pharmacology

Magnesium is important as a cofactor in many enzymatic reactions in the body involving protein synthesis and carbohydrate metabolism (at least 300 enzymatic reactions require magnesium). Actions on lipoprotein lipase have been found to be important in reducing serum cholesterol and on sodium/potassium ATPase in promoting polarization (eg, neuromuscular functioning).

Absorption

Oral: Up to 30%

Excretion

Urine (IOM 1997); feces (as unabsorbed drug)

Use: Labeled Indications

Dietary supplement; relief of acid indigestion and upset stomach; short-term treatment of occasional constipation

Contraindications

There are no contraindications in the manufacturer’s labeling

Dosing: Adult

Dietary Reference Intake for Magnesium: Dosage is in terms of elemental magnesium (IOM, 1997): Oral:

RDA:

19-30 years:

Females: 310 mg daily

Pregnant females: 350 mg daily

Lactation: 310 mg daily

Males: 400 mg daily

≥31 years:

Females: 320 mg daily

Pregnant females: 360 mg daily

Lactation: 320 mg daily

Males: 420 mg daily

OTC labeling:

Antacid (dosage in terms of magnesium oxide salt): Adults: Oral: Tablet: 1-2 tablets (400-800 mg) daily or in divided doses; maximum: 2 tablets daily

Dietary supplement (dosage in terms of magnesium oxide salt): Adults: Oral:

Mag-Ox 400®: Two tablets (800 mg) daily with food (maximum: 2 tablets/24 hours)

Uro-Mag®: 3-4 capsules (420-560 mg) daily with food

Laxative (dosage in terms of elemental magnesium): Children ≥12 years, Adolescents, and Adults: Oral: Caplet: 2-4 caplets (1000-2000 mg) at bedtime or in divided doses

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Dietary Reference Intake for Magnesium: Dosage is in terms of elemental magnesium (IOM, 1997): Oral:

Children:

1-6 months: Adequate intake: 30 mg daily

7-12 months: Adequate intake: 75 mg daily

1-3 years: RDA: 80 mg daily

4-8 years: RDA: 130 mg daily

9-13 years: RDA: 240 mg daily

14-18 years: RDA:

Females: 360 mg daily

Pregnant females: 400 mg daily

Lactation: 360 mg daily

Males: 410 mg daily

OTC labeling:

Laxative (dosage in terms of elemental magnesium): Children ≥12 years and Adolescents: Oral: Refer to adult dosing.

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer’s labeling; however, magnesium is renally excreted. Use with caution; accumulation in renal impairment may lead to magnesium toxicity.

Administration

Administer at least 2 hours apart from other medications. When used as a laxative, administer with at least 8 oz of water.

Dietary Considerations

Should be taken with food and at least 8 oz of water. Whole grains, legumes, and dark-green leafy vegetables are dietary sources of magnesium.

Storage

Store at controlled room temperature. Protect from moisture.

Drug Interactions

Alfacalcidol: May increase the serum concentration of Magnesium Salts. Consider therapy modification

Alpha-Lipoic Acid: Magnesium Salts may decrease the absorption of Alpha-Lipoic Acid. Alpha-Lipoic Acid may decrease the absorption of Magnesium Salts. Consider therapy modification

Bisphosphonate Derivatives: Magnesium Salts may decrease the serum concentration of Bisphosphonate Derivatives. Management: Avoid administration of oral magnesium salts within: 2 hours before or after tiludronate/clodronate/etidronate; 60 minutes after oral ibandronate; or 30 minutes after alendronate/risedronate. Exceptions: Pamidronate; Zoledronic Acid. Consider therapy modification

Calcitriol (Systemic): May increase the serum concentration of Magnesium Salts. Management: Consider using a non-magnesium-containing antacid or phosphate-binding product in patients also receiving calcitriol. If magnesium-containing products must be used with calcitriol, serum magnesium concentrations should be monitored closely. Consider therapy modification

Calcium Channel Blockers: May enhance the adverse/toxic effect of Magnesium Salts. Magnesium Salts may enhance the hypotensive effect of Calcium Channel Blockers. Monitor therapy

Calcium Polystyrene Sulfonate: Laxatives (Magnesium Containing) may enhance the adverse/toxic effect of Calcium Polystyrene Sulfonate. More specifically, concomitant use of calcium polystyrene sulfonate with magnesium-containing laxatives may result in metabolic alkalosis or with sorbitol may result in intestinal necrosis. Management: Avoid concomitant use of calcium polystyrene sulfonate (rectal or oral) and magnesium-containing laxatives. Avoid combination

Deferiprone: Magnesium Salts may decrease the serum concentration of Deferiprone. Management: Separate administration of deferiprone and oral medications or supplements that contain polyvalent cations by at least 4 hours. Consider therapy modification

Dolutegravir: Magnesium Salts may decrease the serum concentration of Dolutegravir. Management: Administer dolutegravir at least 2 hours before or 6 hours after oral magnesium salts. Consider therapy modification

Doxercalciferol: May enhance the hypermagnesemic effect of Magnesium Salts. Management: Consider using a non-magnesium-containing antacid or phosphate-binding product in patients also receiving doxercalciferol. If magnesium-containing products must be used with doxercalciferol, serum magnesium concentrations should be monitored closely. Consider therapy modification

Eltrombopag: Magnesium Salts may decrease the serum concentration of Eltrombopag. Management: Administer eltrombopag at least 2 hours before or 4 hours after oral administration of any magnesium-containing product. Consider therapy modification

Gabapentin: Magnesium Salts may enhance the CNS depressant effect of Gabapentin. Specifically, high dose intravenous/epidural magnesium sulfate may enhance the CNS depressant effects of gabapentin. Magnesium Salts may decrease the serum concentration of Gabapentin. Management: Administer gabapentin at least 2 hours after oral magnesium salts administration. Monitor patients closely for evidence of reduced response to gabapentin therapy. Monitor for CNS depression if high dose IV/epidural magnesium sulfate is used. Consider therapy modification

Levothyroxine: Magnesium Salts may decrease the serum concentration of Levothyroxine. Management: Separate administration of oral levothyroxine and oral magnesium salts by at least 4 hours. Consider therapy modification

Multivitamins/Fluoride (with ADE): Magnesium Salts may decrease the serum concentration of Multivitamins/Fluoride (with ADE). Specifically, magnesium salts may decrease fluoride absorption. Management: To avoid this potential interaction separate the administration of magnesium salts from administration of a fluoride-containing product by at least 1 hour. Consider therapy modification

Mycophenolate: Magnesium Salts may decrease the serum concentration of Mycophenolate. Management: Separate doses of mycophenolate and oral magnesium salts. Monitor for reduced effects of mycophenolate if taken concomitant with oral magnesium salts. Consider therapy modification

Neuromuscular-Blocking Agents: Magnesium Salts may enhance the neuromuscular-blocking effect of Neuromuscular-Blocking Agents. Monitor therapy

Phosphate Supplements: Magnesium Salts may decrease the serum concentration of Phosphate Supplements. Management: This applies only to oral phosphate and magnesium administration. Administer oral phosphate supplements at least 1 hour before, or 2 hours after, oral magnesium salt administration. Exceptions: Sodium Glycerophosphate Pentahydrate. Consider therapy modification

Quinolone Antibiotics: Magnesium Salts may decrease the serum concentration of Quinolone Antibiotics. Management: Administer oral quinolones at least several hours before (4 h for moxi- and sparfloxacin, 2 h for others) or after (8 h for moxi-, 6 h for cipro-, 4 h for lome-, 3 h for gemi-, and 2 h for levo-, nor-, or ofloxacin or nalidixic acid) oral magnesium salts. Exceptions: LevoFLOXacin (Oral Inhalation). Consider therapy modification

Raltegravir: Magnesium Salts may decrease the serum concentration of Raltegravir. Management: Avoid the use of oral / enteral magnesium salts with raltegravir. No dose separation schedule has been established that adequately reduces the magnitude of interaction. Avoid combination

Sodium Polystyrene Sulfonate: Laxatives (Magnesium Containing) may enhance the adverse/toxic effect of Sodium Polystyrene Sulfonate. More specifically, concomitant use of sodium polystyrene sulfonate with magnesium-containing laxatives may result in metabolic alkalosis or with sorbitol may result in intestinal necrosis. Management: Avoid concomitant use of sodium polystyrene sulfonate (rectal or oral) and magnesium-containing laxatives. Avoid combination

Tetracycline Derivatives: Magnesium Salts may decrease the absorption of Tetracycline Derivatives. Only applicable to oral preparations of each agent. Consider therapy modification

Trientine: May decrease the serum concentration of Magnesium Salts. Magnesium Salts may decrease the serum concentration of Trientine. Consider therapy modification

Adverse Reactions

Frequency not defined: Gastrointestinal: Diarrhea (excessive oral doses)

Warnings/Precautions

Disease-related concerns:

• Acid indigestion/upset stomach (self-medication, OTC use): Appropriate use: For occasional use only; serious side effects may occur with prolonged use. For use only under the supervision of a physician in patients with kidney dysfunction or who are pregnant or breast-feeding. Unless directed by a physician, do not use for >2 weeks or exceed the recommended daily dose.

• Constipation (self-medication, OTC use): Appropriate use: For occasional use only; serious side effects may occur with prolonged use. For use only under the supervision of a physician in patients with kidney dysfunction, sodium- or magnesium-restricted diets, abdominal pain/nausea/vomiting,a sudden change in bowel habits which has persisted for >2 weeks, or who are pregnant or breast-feeding. If rectal bleeding develops or a bowel movement does not occur after use, discontinue use and consult healthcare provider.

• Neuromuscular disease: Use with extreme caution in patients with myasthenia gravis or other neuromuscular disease.

• Renal impairment: Use with caution in patients with renal impairment; accumulation of magnesium may lead to magnesium intoxication.

Pregnancy Considerations

Magnesium crosses the placenta; serum concentrations in the fetus are similar to those in the mother (Idama, 1998; Osada, 2002)

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Have patient report immediately to prescriber severe diarrhea (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

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