Pharm
Magnesium Sulfate
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Magnesium Sulfate
, Magnesium Supplementation, Magnesium Replacement
Mechanism
See
Magnesium
Indications
Hypomagnesemia
Arrhythmia
Treatment and Prevention
Torsades de Pointes
Rapid
Atrial Fibrillation
Acute
Myocardial Infarction
Arrhythmia
prevention (variable efficacy)
Preeclampsia
(
Pregnancy Induced Hypertension
)
Preterm Labor
(not effective)
Contraindications
Myasthenia Gravis
Impaired
Renal Function
Preparations
Oral
Magnesium
Oxide 400 mg tablet (61% elemental = 242 mg/tablet)
Dosing: Take 2 orally daily
Magnesium Hydroxide
(
Milk of Magnesia
) 400 mg/5ml (42% elemental = 167 mg/5 ml)
Dosing: 5 to 15 ml up to qid as needed for
Constipation
Additional: 1 ml = 0.3 mEq
Magnesium
Magnesium Citrate
290 mg/5ml (16% elemental = 48 mg/5ml)
Dosing: Up to 1 bottle (120-300 ml)
Also contains 13 mg potasssium per 5 ml
Magnesium
Gluconate 500 mg tablet (5% elemental = 27 mg/tablet)
Dosing: 1-2 tablets orally daily
Magnesium
Chloride 535 mg tablet (12% elemental = 64 mg/tablet)
Dosing: 2 tablets once daily
Magnesium Sulfate (Epsom Salts) 98.6 mg in 1 gram salts (10% elemental)
Dosing: 2-4 teaspoons in 8 oz water up to twice daily as needed for
Constipation
Magnesium
Lactate (Mag-Tab) 84 mg tablet (12% elemental = 84 mg)
Dosing: 1-2 tablets every 12 hours
Magnesium
Aspart
ate Hydroxide (Maginex) 1230 mg granules (10% elemental = 122 mg)
Dosing: Take mixed in 4 ounces water up to three times daily
Parenteral (IV or IM): Magnesium Sulfate (MgSO4)
Magnesium Sulfate is 10% elemental (1 gram
Magnesium
per 100 ml solution)
One gram MgSO4 contains 8.12 meq
Magnesium
One ml MgSO4 50% Solution = 4 meq
Magnesium
One ml MgSO4 10% Solution = 0.8 meq
Magnesium
General Pointers
Do NOT exceed 100 meq/day
Adjust replacement for decreased
Renal Function
Dosing
Oral
Constipation
See oral preparations above for dosing
Most common use of
Magnesium
containing compounds
Recommended Daily Allowance (adults)
Women: 310 mg/day (320 mg/day if over age 30 years)
Men: 400 mg/day (420 mg/day if over age 30 years)
Magnesium
Deficiency
No standardization for diagnosis or for oral replacement
Migraine Headache Prophylaxis
(single study from Germany)
Trimagnesium Dicitrate 600 mg orally daily
Peikert (1996) Cephalgia 16(4): 257-63 [PubMed]
Dosing
IV Dosing of Magnesium Sulfate
Replacement of documented
Magnesium
deficiency
MgSO4 0.5-1.0 grams/hour (4-8 meq/hour) for 24 hours
Preeclampsia
or
Pregnancy Induced Hypertension
Preparation
Magnesium Sulfate 5 grams in 250 ml D5W (20 mg/ml)
Final concentration: 2 grams/hour = 100 ml/hour
Load: 4-6 grams MgSO4 in 100 ml IV over 20-30 minutes
Maintenance: 2-3 grams MgSO4 per hour
Continue until diuresis or about 24 hours postpartum
See monitoring in obstetrics below
Preterm Labor
(not effective)
Same doses as in
Preeclampsia
Does not prevent preterm birth
Gyetvai (1999) Obstet Gynecol 94:869-77 [PubMed]
Maintenance in prolonged IV fluid
Add 1-2 grams (2-4 ml 50% MgSO4) to total IVF per day
Delivers 0.3 to 0.7 meq per hour
Arrhythmia
Prepare 1-2 grams (2-4 ml 50% MgSO4) in 10 ml D5W
Ventricular Tachycardia
: 1-2 g MgSO4 IV over 1-2 min
Ventricular Fibrillation
: 1-2 g MgSO4 IV Push
Torsades de Pointes
: 1-2 g (up to 10 g) MgSO4 IV
Atrial Fibrillation
: 1.2 to 2 grams over 30 minutes
Asthma
Single dose: 25-50 mg/kg for acute severe
Asthma Exacerbation
in age under 18 years
Drug Interactions
Increased
Magnesium
levels with drugs that reduce urinary excretion
Calcitonin
Glucagon
Potassium-Sparing Diuretic
s
Drugs with absorption effected by concurrent
Magnesium
Aminoglycoside
s
Bisphosphonates
Calcium Channel Blocker
s
Fluoroquinolone
s
Skeletal Muscle Relaxant
s
Tetracycline
s
Adverse Effects (see level related effects below)
See
Hypermagnesemia
Too rapid Magnesium Sulfate administration
Flushing
Sweating
Mild
Bradycardia
Hypotension
Monitoring
Obstetrics protocol in
Severe Preeclampsia
Vital Sign
s and Reflexes
First hour: Check every 15 minutes
Later: Monitor
Vital Sign
s every hour
Intake and
Urine Output
Consider
Foley Catheter
Fluid restrict to 2400 cc per 24 hours
Examination
Mental status
Lung Exam
and
Respiratory Rate
Urine Output
Deep Tendon Reflex
es
Check
Serum Magnesium
Level
See also
Serum Magnesium
and
Hypermagnesemia
Obtain 6 hours and 12 hours after MgSO4 load (and then every 6 hours)
Serum Magnesium
level indications (not indicated in normal
Renal Function
, DTRs, normal
Urine Output
)
Absent
Deep Tendon Reflex
es
Decreased
Urine Output
Elevated
Serum Creatinine
Indications to stop
Magnesium
and check level immediately
Urine Output
<30 ml/hour
Respiratory Rate
<12 per minute
Loss of
Deep Tendon Reflex
es
Management
Antidote for
Magnesium
Toxicity
Calcium Gluconate
1 gram IV slowly over 2-3 minutes
References
Guerrera (2009) Am Fam Physician 80(2): 157-62 [PubMed]
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