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Medication Safety Issues
Sound-alike/look-alike issues:
Magnesium sulfate may be confused with manganese sulfate, morphine sulfate
MgSO4 is an error-prone abbreviation (mistaken as morphine sulfate)
High alert medication: The Institute for Safe Medication Practices (ISMP) includes this medication (I.V. formulation) among its list of drugs which have a heightened risk of causing significant patient harm when used in error.
Pronunciation
(mag NEE zhum SUL fate)
Index Terms
Generic Available
Yes
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 levels 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 levels 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 levels closely.
Dosage form specific issues:
• Aluminum: Solutions may contain aluminum; toxic levels may occur following prolonged administration in premature neonates or patients with renal impairment.
Other warnings/precautions:
•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 level, 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 levels 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
Bisphosphonate Derivatives: Magnesium Salts may decrease the absorption of Bisphosphonate Derivatives. Only oral magnesium salts are of concern. 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
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
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
Ketorolac: 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 absorption of Mycophenolate. This only applies to oral magnesium salts. Risk D: Consider therapy modification
Neuromuscular-Blocking Agents: Magnesium Salts may enhance the neuromuscular-blocking effect of Neuromuscular-Blocking Agents. Only of concern in patients with increased serum magnesium concentrations. Risk C: Monitor therapy
Phosphate Supplements: Magnesium Salts may decrease the absorption of Phosphate Supplements. 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
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: May decrease the serum concentration of Magnesium Salts. Magnesium Salts may decrease the serum concentration of Trientine. Risk D: Consider therapy modification
Ethanol/Nutrition/Herb Interactions
Ethanol: Magnesium may enhance the CNS depressant effect of alcohol (ethyl).
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.
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 levels may be transiently normal for a few hours after a dose is given, therefore, aim for consistently high normal serum levels 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 (faster in cardiac arrest); maximum single dose: 2000 mg
Adults:
Mild deficiency: I.M.: 1 g every 6 hours for 4 doses, or as indicated by serum magnesium levels
Severe deficiency:
I.M.: Up to 250 mg/kg within a 4-hour period
I.V.: Severe, nonlife-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).
Arrhythmia (ACLS guidelines, 2005), hypomagnesemia-induced (life-threatening): 1-2 g over 5-20 minutes (torsades with cardiac arrest) or over 5-60 minutes (symptomatic arrhythmias without cardiac arrest)
Seizures, hypomagnesemia-induced: 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 continous 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 continous 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: Adults: I.V.:
Pulseless: 1-2 g over 5-20 minutes
With pulse: 1-2 g over 5-60 minutes. Note: Slower administration preferable for stable patients.
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 IVP, IVPB or I.V.; when giving I.V. push, must dilute first and should not be given any faster than 150 mg/minute. 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, calcium, and potassium levels; renal function during administration
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
Assess other medications patient may be taking for effectiveness and interactions. Assess results of laboratory tests, therapeutic effect, and adverse/toxic effects. Assess knowledge/teach patient proper use, appropriate interventions to reduce side effects, and adverse symptoms to report.
When administered parenterally, monitor serum magnesium level, respiratory rate, deep tendon reflex, and renal function.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Infusion [premixed in D5W]: 10 mg/mL (100 mL); 20 mg/mL (500 mL)
Infusion [premixed in water for injection]: 40 mg/mL (100 mL, 500 mL, 1000 mL); 80 mg/mL (50 mL)
Injection, solution: 500 mg/mL (2 mL, 10 mL, 20 mL, 50 mL)
Powder, oral/topical: Magnesium sulfate USP (227 g, 454 g, 480 g, 1810 g, 1920 g, 2720 g)
Pricing: U.S. (www.drugstore.com)
Solution (Magnesium Sulfate)
50% (50): $22.99
References
“2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care,” Circulation, 2005, 112(24 Suppl):1-211.
“ACOG Practice Bulletin. Diagnosis and Management of Preeclampsia and Eclampsia. Number 33, January 2002,” Obstet Gynecol, 2002, 99(1):159-67.
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.
“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.
Dube L and Granry JC, “The Therapeutic Use Of Magnesium In Anesthesiology, Intensive Care And Emergency Medicine: A Review,” Can J Anaesth, 2003, 50(7):732-46.
Ferroggiaro A, Walther JM, and Cairns CB, “High Doses of Magnesium Impair Cardiac Oxidative Metabolism,” Acad Emerg Med, 1995, 2:423-9.
Ford DC, Leist ER and Phelps SJ, Guidelines for Administration of Intravenous Medications to Pediatric Patients, 3rd ed, Bethesda, MD: American Society of Hospital Pharmacists, 1988, 49.
Gums JG, “Clinical Significance of Magnesium: A Review,” Drug Intell Clin Pharm, 1987, 21(3):240-6.
Gums JG, “Magnesium in Cardiovascular and Other Disorders,” Am J Health Sys Pharm, 2004, 61(15): 1569-76.
Idama TO and Lindow SW, “Magnesium Sulphate: A Review of Clinical Pharmacology Applied to Obstetrics,” Br J Obstet Gynaecol, 1998, 105(3):260-8.
Institute for Safe Medication Practice, “Preventing Magnesium Toxicity in Obstetrics,” ISMP Acute Care Medication Safety Alert, October 20, 2005. Available online at http://www.ismp.org/Newsletters/acutecare/articles/20051020.asp.
Kaeser HE, “Drug-Induced Myasthenia Gravis,” Acta Neurol Scand Suppl, 1984, 100:39-47.
Lucas MJ, Leveno KJ, and Cunningham FG, “A Comparison of Magnesium Sulfate With Phenytoin for the Prevention of Eclampsia,” N Engl J Med, 1995, 333(4):201-5.
Mirtallo J, Canada T, Johnson D, et al, “Safe Practices for Parenteral Nutrition,” JPEN J Parenter Enteral Nutr, 2004, 28(6):39-70.
National Asthma Education and Prevention Program Coordinating Committee, “Expert Panel Report 3 (EPR 3): Guidelines for the Diagnosis and Management of Asthma,” 2007. Available online at http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.htm. Last accessed October 8, 2007.
Nichols B, “Minerals,” Pediatrics, Norwalk, CT: Appleton & Lange, 1987, 176-7.
Vissers R and Purssell R, “Iatrogenic Intravenous Magnesium Overdose Causing Cardiac Arrest,” J Toxicol Clin Toxicol, 1995, 33(5):489.
Worthley LT, “Lithium Toxicity and Refractory Cardiac Arrhythmia Treated With Intravenous Magnesium,” Anaesth Intensive Care, 1974, 4:357-60.
International Brand Names
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Last full review/revision October 2009
Content last modified October 2009
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