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Magnesium sulfate, magnesium sulphate
Mineral, anticonvulsant, antiarrhythmic, bronchodilator

Parenteral use of magnesium sulfate in the presence of renal insufficiency may lead to magnesium intoxication. Parenteral administration of the drug is contraindicated in patients with heart block or myocardial damage , and myasthenia gravis.

  • Treatment of preeclampsia and eclampsia[1-3,12,13 ]

    Continuous Intravenous Infusion

      Magnesium sulfate 4-g to 6-g loading dose diluted in 100 mL fluid  administered intravenously over 15 minutes, followed by continuous intravenous infusion at 1 to 2 g per hour. Discontinue 24 hours after delivery or last seizure.

      OR

    Intermittent Intramuscular Injections

      Magnesium sulfate 4 g as 20% solution intravenously at rate not to exceed 1g/min, followed immediately by magnesium sulfate 5 g (as 50%  solution) into the upper outer quadrant of each buttock. then 5g in  alternate buttocks every 4 hours . Use 20 gauge, 3 inch long needle. Discontinue 24 hours after delivery or last seizure.

    For Recurrent Convulsions (either IV or IM regimen)

      If convulsions persist after 15 min, give up to 2  gram more intravenously as a 20% solution at a rate not to exceed 1g/min. If the woman is large (> 70 kg) then an additional 2 grams may be given slowly [1-3].
       
    Only give the next IM dose, or only continue the IV infusion if:
    • Respiratory rate > 16/min
    • Urine output > 25 ml/h
    • Patellar reflexes are present
       
    If urine output < 100 ml in 4 h and there are no other signs of magnesium toxicity, reduce the next IM dose of magnesium sulfate to 2.5 g, or the IV infusion to 0.5 g/h.[3]

    Magnesium level monitoring [1,3, 4]

    Measure serum magnesium every 4 to 6 hours if  if serum creatinine is >= 1mg/dL[1]

    Serum magnesium  

    Effect

    >mmol/L mEq/L mg/dL
    2 to 3.5 4 - 7 5 9 Therapeutic range
    > 3.5 > 7 > 9 Loss of patellar reflexes
    > 5 > 10 > 12 Respiratory paralysis
    > 12.5 > 25 > 30 Cardiac arrest
     

    If patellar reflexes are depressed and respiration is normal, withhold further doses of magnesium sulfate until the reflexes return and request magnesium level.

    If there is concern about respiratory depression , stop magnesium, give oxygen by mask and give:

    Calcium gluconate (10mL of 10% solution over 10 minutes)  [5]


  • Antenatal neuroprotection

    Fetal exposure to magnesium sulfate in women at risk of preterm delivery reduces the risk of cerebral palsy without increasing the risk of death. The appropriate total dosage, infusion period, need for retreatment and therapeutic window for neuroprotection are not known [14,15]. Two regimens are presented below.

    Loading dose of 4 g by infusion pump over 30 minutes, followed by continuous intravenous infusion at 1 g per until birth. Magnesium sufate should be discontinued if delivery is no longer imminent or a maximum of 24 hours of therapy has been administered [16]

    Loading dose of 6 g by infusion pump over 20 to 30 minutes, followed by continuous intravenous infusion at 2 g per hour. Discontinue infusion after 12 hours if delivery is no longer considered imminent. If threat of delivery recurs after 6 or more hours, then re-bolus [6].

 


  • Treatment of torsades de pointes associated with VF/pulseless VT cardiac [7] treat hypokalemia if present

    Magnesium sulfate 1 to 2 g diluted in 10 mL D5W IV/IO push over 5 to 20 minutes

     

  • Treatment of torsades de pointes in patient with pulses [7]

    Magnesium sulfate 1 to 2 g diluted in 50 to 100 mL D5W IV over 5 to 60 minutes
     


  • Severe acute asthma [7,8]

     1.2 to 2 g IV given over 20 minutes


Severe hypomagnesemia (< 1 mEq/L)

2 grams of magnesium sulfate in 100 ml of D5W intravenous over 5 to 10 min followed by a continuous infusion of 4 to 6 g/d for 3 to 5 d if renal function is normal.

Mild hypomagnesemia (1.1 to 1.4 mEq/L)

6 to 12 g daily and continue 3 to 5 days after body stores have been replenished


Supplied As [10]
(Magnesium sulfate 50% single-dose containers 5 g/10 mL(4 mEq/mL) must be diluted to a concentration of 20% or less prior to I.V. infusion


 

REFERENCES
1. Cunningham FG,  Leveno KJ, Bloom SL, Hauth JC, Rouse DJ, Spong CY Pregnancy Hypertension. In: Williams obstetrics. 23rd ed. New York: McGraw-Hill, 2010:737
2. Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial. Lancet 1995; 345(8963):
3. Duley L.Magnesium sulphate regimens for women with eclampsia: messages from the Collaborative Eclampsia Trial.  Br J Obstet Gynaecol. 1996 Feb;103(2):103-5. PMID:8616123
4.Lu JF, Nightingale CH. Magnesium sulfate in eclampsia and pre-eclampsia: pharmacokinetic principles. Clin Pharmacokinet. 2000 Apr;38(4):305-14. PMID:10803454
5.RCOG Guideline number 10(A) The Management of Severe Pre-eclampsia/eclampsia March 2006
http://www.rcog.org.uk/womens-health/clinical-guidance/management-severe-pre-eclampsiaeclampsia-green-top-10a Accessed 7/16/2010
  6.Rouse DJ, et al. Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units Network..A randomized, controlled trial of magnesium sulfate for the prevention of cerebral palsy. N Engl J Med. 2008 Aug 28;359(9):895-905.PMID:18753646
7. ECC Committee, Subcommittees and Task Forces of the American Heart Association. 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2005 Dec 13;112(24 Suppl):IV1-203. Epub 2005 Nov 28. PMID: PMID:16314375 http://circ.ahajournals.org/content/vol112/24_suppl/
8. Rowe BH, et al. Magnesium sulfate for treating exacerbations of acute asthma in the emergency department.Cochrane Database Syst Rev. 2000;(2):CD001490.
9. Martin KJ, et al., Clinical consequences and management of hypomagnesemia.J Am Soc Nephrol. 2009 Nov;20(11):2291-5. Epub 2008 Jan 30. PMID:18235082
10. Gnerlich JL and Buchman TG. Fluids, Electrolyte, and Acid-Base Disorders In:Klingensmith ME et al., ed. The Washington Manual of Surgery, Fifth Edition Philadelphia: Lippincott, Williams and Wilkins,2008: 82
11.Package insert Hospira, Inc . May 2010
http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=18492
12.Cahill AG, et al., Magnesium for seizure prophylaxis in patients with mild preeclampsia.Obstet Gynecol. 2007 Sep;110(3):601-7.PMID: 17766606
13. Alexander JM, Selective magnesium sulfate prophylaxis for the prevention of eclampsia in women with gestational hypertension. Obstet Gynecol. 2006 Oct;108(4):826-32. PMID:17012442  
14. Costantine MM, Effects of antenatal exposure to magnesium sulfate on neuroprotection and mortality in preterm infants: a meta-analysis. Obstet Gynecol. 2009 Aug;114(2 Pt 1):354-64.PMID:19622997  
15. American College of Obstetricians and Gynecologists Committee on Obstetric Practice; Society for Maternal-Fetal Medicine.Committee Opinion No. 455: Magnesium sulfate before anticipated preterm birth for neuroprotection.
Obstet Gynecol. 2010 Mar;115(3):669-71.PMID:20177305  
16. Magee L, et al. SOGC Clinical Practice Guideline. Magnesium sulphate for fetal neuroprotection.
J Obstet Gynaecol Can. 2011 May;33(5):516-29.PMID:21639972  
http://www.sogc.org/guidelines/documents/gui258CPG1106E.pdf
 

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