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Pronunciation
(mag NEE zhum SUL fate)
Generic Available (U.S.)
Yes
Index Terms
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Treatment and prevention of hypomagnesemia; prevention and treatment of seizures in severe pre-eclampsia or eclampsia, pediatric acute nephritis; torsade de pointes; treatment of cardiac arrhythmias (VT/VF) caused by hypomagnesemia; soaking aid
Use: Unlabeled/Investigational
Asthma exacerbation (life-threatening)
Pregnancy Risk Factor
A/C (manufacturer dependent)
Pregnancy Considerations
Magnesium crosses the placenta; serum concentrations in the fetus correlate with those in the mother. Magnesium sulfate is used during pregnancy for the treatment of eclampsia and severe pre-eclampsia.
Lactation
Enters breast milk/compatible
Breast-Feeding Considerations
Magnesium is found in breast milk. The amount is not influenced by dietary intake under normal conditions. In women receiving parenteral magnesium sulfate for the treatment of eclampsia, magnesium concentrations in breast milk returned to normal 24 hours following discontinuation of treatment.
Contraindications
Hypersensitivity to any component of the formulation; heart block; myocardial damage
Warnings/Precautions
Disease-related concerns:
• 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.
Special populations:
• Obstetrics: Vigilant monitoring and safe administration techniques (ISMP Medication Safety Alert, 2005) recommended to avoid potential for errors resulting in toxicity. Monitor patient and fetal status, and serum magnesium concentrations closely.
Dosage form specific issues:
• Aluminum: Solutions may contain aluminum; toxic concentrations may occur following prolonged administration in premature neonates or patients with renal impairment.
Other warnings/precautions:
• Appropriate use: Irregular/Polymorphic VT (with normal baseline QT interval): Unlikely to effectively terminate.
•Electrolyte abnormalities: Concurrent hypokalemia or hypocalcemia can accompany a magnesium deficit. Hypomagnesemia is frequently associated with hypokalemia and requires correction in order to normalize potassium.
• Parenteral administration: Monitor serum magnesium concentration, respiratory rate, blood pressure, deep tendon reflex, and renal function when administered parenterally, particularly with repeated dosing; magnesium toxicity can lead to fatal cardiovascular arrest and/or respiratory paralysis.
Adverse Reactions
Adverse effects on neuromuscular function may occur at lower concentrations in patients with neuromuscular disease (eg, myasthenia gravis).
Frequency not defined:
Cardiovascular: Flushing (I.V.; dose related), hypotension (I.V.; rate related), vasodilation (I.V.; rate related)
Gastrointestinal: Diarrhea
Drug Interactions
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
Alfacalcidol: May increase the serum concentration of Magnesium Salts. Risk D: 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 ibandronate; or 30 minutes after alendronate/risedronate. Exceptions: Pamidronate; Zoledronic Acid. Risk D: Consider therapy modification
Calcitriol: May increase the serum concentration of Magnesium Salts. Risk D: 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. Risk C: Monitor therapy
Calcium Polystyrene Sulfonate: Laxatives 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 or sorbitol. Risk X: Avoid combination
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Exceptions: Levocabastine (Nasal). Risk C: Monitor therapy
Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (e.g., opioids, barbiturates) with concomitant use. Risk D: Consider therapy modification
Eltrombopag: Magnesium Salts may decrease the serum concentration of Eltrombopag. Management: Separate administration of eltrombopag and any polyvalent cation (e.g., magnesium-containing products) by at least 4 hours. Risk D: Consider therapy modification
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Management: For patients being treated with hydroxyzine, a reduction in the dose of any other CNS depressants that are to be used in combination is recommended. With concurrent use, monitor patients closely for excessive response to the combination. Risk D: Consider therapy modification
Ketorolac: May diminish the therapeutic effect of Anticonvulsants. Risk C: Monitor therapy
Ketorolac (Nasal): May diminish the therapeutic effect of Anticonvulsants. Risk C: Monitor therapy
Ketorolac (Systemic): May diminish the therapeutic effect of Anticonvulsants. Risk C: Monitor therapy
Mefloquine: May diminish the therapeutic effect of Anticonvulsants. Mefloquine may decrease the serum concentration of Anticonvulsants. Management: Mefloquine is contraindicated for malaria prophylaxis in persons with a history of convulsions. Monitor anticonvulsant concentrations and treatment response closely with concurrent use. Risk D: Consider therapy modification
Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce adult dose of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established. Risk D: 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. Risk D: Consider therapy modification
Neuromuscular-Blocking Agents: Magnesium Salts may enhance the neuromuscular-blocking effect of Neuromuscular-Blocking Agents. Risk C: Monitor therapy
Phosphate Supplements: Magnesium Salts may decrease the serum concentration of Phosphate Supplements. Management: Administer oral phosphate supplements at least 1 hour before, or 2 hours after, oral magnesium salt administration. Exceptions: Potassium Phosphate. Risk D: Consider therapy modification
Quinolone Antibiotics: Magnesium Salts may decrease the absorption of Quinolone Antibiotics. Of concern only with oral administration of both agents. Risk D: Consider therapy modification
Selective Serotonin Reuptake Inhibitors: CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced. Risk C: Monitor therapy
Sodium Polystyrene Sulfonate: Laxatives 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 or sorbitol. Risk X: Avoid combination
Tetracycline Derivatives: Magnesium Salts may decrease the absorption of Tetracycline Derivatives. Only applicable to oral preparations of each agent. Risk D: Consider therapy modification
Trientine: Magnesium Salts may decrease the serum concentration of Trientine. Trientine may decrease the serum concentration of Magnesium Salts. Risk D: Consider therapy modification
Ethanol/Nutrition/Herb Interactions
Ethanol: May increase CNS depression; monitor for increased effects with coadministration. Caution patients about effects.
Storage
Prior to use, store at room temperature of 20°C to 25°C (68°F to 77°F). Refrigeration of solution may result in precipitation or crystallization.
Compatibility
Stable in D5W, LR, NS; incompatible with fat emulsion 10%
Y-site administration: Compatible: Acyclovir, aldesleukin, amifostine, amikacin, ampicillin, aztreonam, cefamandole, cefazolin, cefoperazone, cefotaxime, cefoxitin, chloramphenicol, cisatracurium, clindamycin, dobutamine, docetaxel, doxorubicin liposome, doxycycline, enalaprilat, erythromycin lactobionate, esmolol, etoposide, famotidine, fludarabine, gatifloxacin, gentamicin, granisetron, heparin, hydrocortisone sodium succinate, hydromorphone, idarubicin, insulin (regular), kanamycin, labetalol, linezolid, meperidine, metronidazole, milrinone, minocycline, morphine, nafcillin, ondansetron, oxacillin, paclitaxel, penicillin G potassium, piperacillin, piperacillin/tazobactam, potassium chloride, propofol, remifentanil, sargramostim, thiotepa, ticarcillin, tobramycin, trimethoprim/sulfamethoxazole, vancomycin, vitamin B complex with C. Incompatible: Alatrofloxacin, amphotericin B cholesteryl sulfate complex, cefepime. Variable (consult detailed reference): Ciprofloxacin.
Compatibility in syringe: Compatible: Metoclopramide. Incompatible: Hydrocortisone sodium succinate.
Compatibility when admixed: Compatible: Calcium gluconate, chloramphenicol, cisplatin, heparin, hydrocortisone sodium succinate, isoproterenol, meropenem, methyldopate, norepinephrine, penicillin G potassium, potassium phosphates, verapamil. Incompatible: Amphotericin B, clindamycin, cyclosporine, dobutamine, polymyxin B sulfate, procaine, sodium bicarbonate.
Mechanism of Action
When taken orally, magnesium promotes bowel evacuation by causing osmotic retention of fluid which distends the colon with increased peristaltic activity; parenterally, magnesium decreases acetylcholine in motor nerve terminals and acts on myocardium by slowing rate of S-A node impulse formation and prolonging conduction time. Magnesium is necessary for the movement of calcium, sodium, and potassium in and out of cells, as well as stabilizing excitable membranes.
Intravenous magnesium may improve pulmonary function in patients with asthma; causes relaxation of bronchial smooth muscle independent of serum magnesium concentration.
Pharmacodynamics/Kinetics
Onset of action: Anticonvulsant: I.M.: 1 hour; I.V.: Immediate
Duration of anticonvulsant activity: I.M.: 3-4 hours; I.V.: 30 minutes
Distribution: Bone (50% to 60%); extracellular fluid (1% to 2%)
Protein binding: 30%, to albumin
Excretion: Urine (as magnesium)
Dosage
Dose represented as magnesium sulfate unless stated otherwise. Note: Serum magnesium is poor reflection of repletional status as the majority of magnesium is intracellular; serum concentrations may be transiently normal for a few hours after a dose is given, therefore, aim for consistently high normal serum concentrations in patients with normal renal function for most efficient repletion.
Note: 1 g of magnesium sulfate = 98.6 mg elemental magnesium = 8.12 mEq elemental magnesium
Hypomagnesemia: Note: Treatment depends on severity and clinical status:
Children: I.V., I.O.: 25-50 mg/kg/dose over 10-20 minutes (over several minutes for torsade de pointes); maximum single dose: 2000 mg (PALS, 2010)
Adults:
Mild deficiency: I.M.: 1 g every 6 hours for 4 doses, or as indicated by serum magnesium concentrations
Severe deficiency:
I.M.: Up to 250 mg/kg within a 4-hour period
I.V.: Severe, non-life-threatening: 1-2 g/hour for 3-6 hours then 0.5-1 g/hour as needed to correct deficiency
Symptomatic deficiency: I.V.: 1-2 g over 5-60 minutes; maintenance infusion may be required to correct deficiency (0.5-1 g/hour).
With polymorphic VT (including torsade de pointes): I.V. push: 1-2 g (ACLS, 2010)
With seizures: I.V.: 2 g over 10 minutes; calcium administration may also be appropriate as many patients are also hypocalcemic
Asthma (life-threatening or severe exacerbation after 1 hour of intensive conventional therapy; unlabeled use): I.V.:
Children: 25-75 mg/kg (maximum: 2 g)
Adults: 2 g
Eclampsia: Adults:
I.V.: 4-5 g infusion; followed by a 1-2 g/hour continuous infusion; or may follow with I.M. doses of 4-5 g in each buttock every 4 hours. Note: Initial infusion may be given over 3-4 minutes if eclampsia is severe; maximum: 40 g/24 hours
ACOG Practice Bulletin 2002: 4-6 g over 15-20 minutes followed by 2 g/hour continuous infusion
Pre-eclampsia (severe): Adults: I.V. 4-5 g infusion; followed by a 1-2 g/hour continuous infusion; or may follow with I.M. doses of 4-5 g in each buttock every 4 hours; maximum: 40 g/24 hour
Torsade de pointes or VF/pulseless VT associated with torsade de pointes (unlabeled use): Adults: I.V., I.O.: 1-2 g over 15 minutes (ACLS, 2010)
Parenteral nutrition supplementation: I.V.:
Children:
<50 kg: 0.3-0.5 mEq elemental magnesium/kg/day
>50 kg: 10-30 mEq elemental magnesium/day
Adults: 8-24 mEq elemental magnesium/day
Soaking aid: Topical: Adults: Dissolve 2 cupfuls of powder per gallon of warm water
RDA:
Children:
1-3 years: 80 mg elemental magnesium/day
4-8 years: 130 mg elemental magnesium/day
9-13 years: 240 mg elemental magnesium/day
14-18 years:
Female: 360 mg elemental magnesium/day
Pregnant female: 400 mg elemental magnesium/day
Male: 410 mg elemental magnesium/day
Adults:
19-30 years:
Female: 310 mg elemental magnesium/day
Pregnant female: 350 mg elemental magnesium/day
Male: 400 mg elemental magnesium/day
≥31 years:
Female: 320 mg elemental magnesium/day
Pregnant female: 360 mg elemental magnesium/day
Male: 420 mg elemental magnesium/day
Dosage adjustment in renal impairment: Clcr <30 mL/minute: Use with caution; monitor for hypermagnesemia; do not exceed 20 g/48 hours as per manufacturer. Close monitoring is required.
Administration: I.M.
A 25% or 50% concentration may be used for adults and dilution to a ≤20% solution is recommended for children
Administration: I.V.
Magnesium should be diluted to a ≤20% solution for I.V. infusion and may be administered I.V. push, IVPB, or continuous I.V. infusion. When giving I.V. push, must dilute first and should not be given any faster than 150 mg/minute; may administer over 1-2 minutes in patients with persistent pulseless VT or VF with known hypomagnesemia (Dager, 2006). ACLS guidelines recommend administration over 15 minutes in patients with torsade de pointes (ACLS, 2010). In patients not in cardiac arrest, hypotension and asystole may occur with rapid administration.
Maximal rate of infusion: 2 g/hour to avoid hypotension; doses of 4 g/hour have been given in emergencies (eclampsia, seizures); optimally, should add magnesium to I.V. fluids, but bolus doses are also effective
Administration: Topical
Dissolve 2 cups of powder per gallon of warm water to use as a soaking aid. To make a compress, dissolve 2 cups of powder per 2 cups of hot water and use a towel to apply as a wet dressing.
Monitoring Parameters
I.V.: Rapid administration: ECG monitoring, vital signs, deep tendon reflexes; magnesium concentrations if frequent or prolonged dosing required particularly in patients with renal dysfunction, calcium, and potassium concentrations
Obstetrics: Patient status including vital signs, oxygen saturation, deep tendon reflexes, level of consciousness, fetal heart rate, maternal uterine activity.
Reference Range
Serum magnesium: 1.5-2.5 mg/dL; slightly different ranges are reported by different laboratories
Dietary Considerations
Whole grains, legumes and dark-green leafy vegetables are dietary sources of magnesium.
Patient Education
Take in divided doses. Report diarrhea (>5 stools/day) or changes in mental function to prescriber.
Anesthesia and Critical Care Concerns/Other Considerations
Clinical Pearls/Comments: Hypomagnesemia can hinder the replenishment of intracellular potassium and should be corrected in order to correct hypokalemia.
Dental Health: Effects on Dental Treatment
Key adverse event(s) related to dental treatment: Magnesium products may prevent GI absorption of tetracyclines by forming a large ionized chelated molecule with the tetracyclines in the stomach. Tetracyclines should be given at least 1 hour before magnesium.
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
May cause sedation or CNS depression
Mental Health: Effects on Psychiatric Treatment
Concurrent use with psychotropics may produce additive CNS depression
Nursing: Physical Assessment/Monitoring
When administered parenterally, monitor serum magnesium concentration, respiratory rate, deep tendon reflex, and renal function.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Infusion, premixed in D5W: 10 mg/mL (100 mL) [equivalent to elemental magnesium 0.99 mg (0.08 mEq)/mL]; 20 mg/mL (500 mL) [equivalent to elemental magnesium 1.97 mg (0.16 mEq)/mL]
Infusion, premixed in water for injection: 40 mg/mL (50 mL, 100 mL, 500 mL, 1000 mL) [equivalent to elemental magnesium 3.94 mg (0.32 mEq)/mL]; 80 mg/mL (50 mL) [equivalent to elemental magnesium 7.89 mg (0.65 mEq)/mL]
Injection, solution: 500 mg/mL (20 mL, 25 mL [DSC]) [equivalent to elemental magnesium 49.3 mg (4.06 mEq)/mL]
Injection, solution [preservative free]: 500 mg/mL (2 mL, 5 mL [DSC], 10 mL, 20 mL, 50 mL) [equivalent to elemental magnesium 49.3 mg (4.06 mEq)/mL]
Powder, oral/topical: USP: 100% (227 g, 454 g, 1810 g, 2720 g)
References
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Bashuk RG and Krendel DA, “Myasthenia Gravis Presenting as Weakness After Magnesium Administration,” Muscle Nerve, 1990, 13(8):708-12.
Bohman VR and Cotton DB, “Supralethal Magnesemia With Patient Survival,” Obstet Gynecol, 1990, 76(5 Pt 2):984-6.
Catanzarite VA, McHargue AM, Sandberg EC, et al, “Respiratory Arrest During Therapy for Premature Labor in a Patient With Myasthenia Gravis,” Obstet Gynecol, 1984, 64(6):819-22.
Chernow B, Smith J, Rainey TG, et al, “Hypomagnesemia: Implications for the Critical Care Specialist,” Crit Care Med, 1982, 10(3):193-6.
Cohen BA, London RS, and Goldstein PJ, “Myasthenia Gravis and Preeclampsia,” Obstet Gynecol, 1976, 48(1 Suppl):35-7.
Dager WE, Sanoski CA, Wiggins BS, et al, “Pharmacotherapy Considerations in Advanced Cardiac Life Support,” Pharmacotherapy, 2006, 26(12):1703-29.
“Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine,” National Academy of Sciences, Washington, DC: National Academy Press, 1997. Available at http://www.nap.edu
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Eagle KA, Guyton RA, Davidoff R, et al, “ACC/AHA 2004 Guideline Update for Coronary Artery Bypass Graft Surgery: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery),” Circulation, 2004, 110(14):e340-437.
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Mirtallo J, Canada T, Johnson D, et al, “Safe Practices for Parenteral Nutrition,” JPEN J Parenter Enteral Nutr, 2004, 28(6):39-70.
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International Brand Names
Lexi-Comp.com
Last full review/revision May 2011
Content last modified May 2011
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