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Magnesium Sulfate

Medically reviewed by Drugs.com. Last updated on Mar 28, 2020.

Pronunciation

(mag NEE zhum SUL fate)

Index Terms

  • Epsom Salts
  • MgSO4 (error-prone abbreviation)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Capsule, Oral:

M2 Magnesium: 100 mg

Magnacaps: 100 mg [corn free, rye free, wheat free]

Generic: 70 mg

Granules, Oral:

Epsom Salt: (454 g, 1810 g, 1816 g [DSC])

GoodSense Epsom Salt: (454 g, 1810 g)

Solution, Injection:

Generic: 50% (10 mL, 20 mL)

Solution, Injection [preservative free]:

Generic: 50% (2 mL, 10 mL, 20 mL, 50 mL)

Solution, Intravenous:

Generic: 4 g/100 mL (100 mL); 1 g/100 mL (100 mL); 2 g/50 mL (50 mL); 20 g/500 mL (500 mL); 4 g/50 mL (50 mL); 40 g/1000 mL (1000 mL)

Solution, Intravenous [preservative free]:

Generic: 1 g/100 mL (100 mL)

Brand Names: U.S.

  • Epsom Salt [OTC]
  • GoodSense Epsom Salt [OTC]
  • M2 Magnesium [OTC]
  • Magnacaps [OTC]

Pharmacologic Category

  • Anticonvulsant, Miscellaneous
  • Electrolyte Supplement, Parenteral
  • Magnesium Salt

Pharmacology

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.

Absorption

Oral: Slow and poor (approximately one-third absorbed)

Distribution

Bone (50% to 60%); extracellular fluid (1% to 2%) (IOM 1997)

Excretion

Urine (as magnesium); feces (as unabsorbed drug)

Onset of Action

Anticonvulsant: IM: 1 hour; Anticonvulsant: IV: Immediate; Laxative: Oral: 0.5 to 6 hours

Duration of Action

Anticonvulsant activity: IM: 3 to 4 hours; IV: 30 minutes

Protein Binding

30%, to albumin

Use: Labeled Indications

Oral: Laxative for the relief of occasional constipation (OTC labeling)

Parenteral: Treatment and prevention of hypomagnesemia; prevention and treatment of seizures in severe preeclampsia or eclampsia, pediatric acute nephritis; treatment of cardiac arrhythmias (VT/VF) caused by hypomagnesemia

Topical: Soaking aid for minor cuts and bruises (OTC labeling)

Off Label Uses

Asthma (acute severe exacerbations)

Based on the National Asthma Education and Prevention Program Coordinating Committee (NAEPP) Expert Panel Report 3 (EPR 3): Guidelines for the Diagnosis and Management of Asthma, magnesium sulfate given as adjunctive therapy for life-threatening asthma or for exacerbations that remain severe after 1 hour of intensive conventional treatment is effective and recommended in the management of this condition. The Global Initiative for Asthma (GINA): Global Strategy for Asthma Management and Prevention guidelines recommend magnesium sulfate be considered for patients with severe exacerbations not responding to initial treatment in an acute care setting, such as an emergency room. Magnesium sulfate is not recommended for routine use [GINA 2020].

Torsades de pointes: Polymorphic VT (with pulse) associated with QT prolongation (torsades de pointes) or VF/pulseless VT associated with torsades de pointes

Based on the American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, magnesium sulfate given for torsades de pointes or VF/pulseless VT associated with torsades de pointes is effective and recommended in the management of this condition.

Contraindications

Hypersensitivity to any component of the formulation; heart block (see Note); myocardial damage; IV use for preeclampsia/eclampsia during the 2 hours prior to delivery (see Note)

Note: Although the manufacturers' labeling for some IV formulations state use in preeclampsia/eclampsia during the 2 hours prior to (cesarean) delivery is contraindicated due to interaction with neuromuscular-blocking agents intraoperatively; stopping magnesium sulfate prior to cesarean delivery in these patients is not recommended and increases the risk of seizure. Instead, magnesium should be continued prior to and during the delivery (ACOG 2013). Additionally, the manufacturers' labeling for some IV formulations contraindicate the use of magnesium sulfate in the setting of heart block; however, the use of magnesium is appropriate in patients with serious conditions requiring magnesium therapy who either have mild degrees of heart block (eg, first degree) or more severe forms of heart block with a temporary or permanent cardiac pacemaker.

Dosing: Adult

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 = magnesium 4.06 mmol

Asthma (acute severe exacerbations) (off-label use): IV: 2 g as a single dose over 20 minutes (GINA 2020; NAEPP 2007); recommended as adjunctive therapy for severe life-threatening exacerbations and for exacerbations that remain severe after 1 hour of intensive conventional therapy (NAEPP 2007).

Constipation (occasional): Oral: 2 to 4 level teaspoons of granules dissolved in 8 ounces of water; may repeat in 6 hours. Do not exceed 2 doses per day.

Eclampsia/preeclampsia: Note: An optimal regimen has not been identified. Close monitoring (including renal function, respiration, and tendonpatellar reflexes) is required and doses should be adjusted to avoid maternal toxicity. Product labeling recommends a maximum dose of 40 g/24 hours; however, this is variable by regimen. Some sources recommend monitoring of plasma magnesium for therapeutic concentrations as well as for the clinical assessment of magnesium toxicity (De Silva 2015; Duley 2010; Long 2017; Pratt 2016).

IV: Initial: 4 to 6 g loading dose over 20 to 30 minutes, followed by 1 to 2 g/hour continuous infusion for at least 24 hours after delivery (ACOG 2020).

IM: Initial: 10 g loading dose administered as 5 g IM in each buttock, then 5 g every 4 hours. Note: Use IM route when unable to establish venous access (ACOG 2020).

Manufacturer's labeling: IV, IM: An initial total dose of 10 to 14 g administered as follows: 4 g IV infusion with simultaneous IM injections of 4 to 5 g in each buttock. After the initial IV/IM doses, may administer a 1 to 2 g/hour continuous infusion or may follow with IM doses of 4 to 5 g into alternate buttocks every 4 hours as necessary.

Hypomagnesemia, treatment: Note: Treatment depends on severity and clinical status. In asymptomatic patients (when oral route is available), oral replacement therapy is a better replacement method than IV administration.

Mild deficiency: IM: 1 g every 6 hours for 4 doses, or as indicated by serum magnesium concentrations

Mild to moderate (serum concentration 1 to 1.5 mg/dL): IV: 1 to 4 g (up to 0.125 g/kg), administer at ≤1 g/hour if asymptomatic; do not exceed 12 g over 12 hours (Kraft 2005). Note: Additional supplementation may be required after the initial dose with replenishment occurring over several days.

Severe deficiency:

IM: Up to 250 mg/kg within a 4-hour period

IV: Severe (<1 mg/dL): 4 to 8 g (up to 0.1875 g/kg), administer at ≤1 g/hour if asymptomatic; in symptomatic patients, may administer ≤4 g over 4-5 minutes (Kraft 2005)

Obesity: Weight >130% of ideal body weight (IBW) or body mass index (BMI) ≥30 kg/m2: When determining maximum per kg dose for replacement, some clinicians suggest using adjusted body weight (AdjBW) (Kraft 2005).

AdjBW (men) = ([wt (kg) -IBW (kg)] x 0.3) + IBW

AdjBW (women) = ([wt (kg) -IBW (kg)] x 0.25) + IBW

Hypomagnesemia, prevention (parenteral nutrition supplementation): IV: 8 to 20 mEq elemental magnesium daily (ASPEN [Mirtallo 2004])

Soaking aid: Topical: Dissolve 2 cupfuls of granules per gallon of warm water; may also soak a towel with the solution to apply as a wet dressing.

Torsades de pointes (off-label use):

Polymorphic VT (with pulse) associated with QT prolongation (torsades de pointes): IV: 1 to 2 g (diluted in 50 to 100 mL D5W) over 15 minutes (range: 5 to 60 minutes); may follow with a continuous IV infusion of 0.5 to 1 g/hour (ACLS [Neumar 2010]; AHA [Hazinski 2015])

VF/pulseless VT associated with torsades de pointes: IV/IO: 1 to 2 g (diluted in 10 mL D5W) administered as a bolus (ACLS [Neumar 2010])

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Note: 1,000 mg of magnesium sulfate = 98.7 mg elemental magnesium = 8.12 mEq elemental magnesium = 4.06 mmol elemental magnesium. Serum magnesium is poor reflection of repletion 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.

Hypomagnesemia: Infants, Children, and Adolescents: Note: Dose depends on clinical condition and serum magnesium concentration.

Dose expressed as magnesium sulfate: IV, Intraosseous: 25 to 50 mg /kg/dose every 6 hours for 2 to 3 doses, then recheck serum concentration; maximum dose: 2,000 mg/dose (AAP [Shenoi 2020]; Kliegman 2020; PALS [Kleinman 2010]).

Dose expressed as elemental magnesium: IV: 2.5 to 5 mg/kg/dose every 6 hours for 2 to 3 doses (Kliegman 2020).

Constipation, occasional: Note: With OTC use, should not exceed recommended treatment duration (7 days) unless directed by health care provider.

Children 6 to <12 years: Oral: 1 to 2 level teaspoons of granules dissolved in 8 ounces of water; may repeat in 4 hours. Do not exceed 2 doses per day.

Children ≥12 years and Adolescents: Oral: 2 to 4 level teaspoons of granules dissolved in 8 ounces of water; may repeat in 4 hours. Do not exceed 2 doses per day.

Parenteral nutrition, maintenance magnesium requirement (ASPEN [Mirtallo 2004]): Dose expressed as elemental magnesium:

Infants and Children ≤50 kg: IV: 0.3 to 0.5 mEq/kg/day as an additive to parenteral nutrition solution.

Children >50 kg and Adolescents: IV: 10 to 30 mEq/day as an additive to parenteral nutrition solution.

Torsade de pointes or ventricular fibrillation/pulseless ventricular tachycardia associated with torsade de pointes: Dose expressed as magnesium sulfate:

Infants, Children, and Adolescents: IV, Intraosseous: 25 to 50 mg/kg/dose; maximum dose: 2,000 mg/dose (PALS [Kleinman 2010]).

Asthma, acute refractory exacerbation: Limited data available: Dose expressed as magnesium sulfate:

IV: Infants, Children, and Adolescents: 50 mg/kg/dose as a single dose (Becker 2019); usual dose range: 25 to 75 mg/kg/dose; maximum dose: 2,000 mg/dose; recommended as adjunctive therapy in severe acute asthma for patients who have life-threatening exacerbations and in those whose exacerbations remain in the severe category after 1 hour of intensive conventional therapy (AAP [Shenoi 2020]; GINA 2020; NAEPP 2007). Efficacy results have been variable in trials; some have shown significant improvement with single doses of 25 mg/kg/dose and 40 mg/kg/dose (Ciarallo 1996; Ciarallo 2000) while others found no statistically significant difference compared to placebo (Scarfone 2000). A pharmacokinetic modeling study of pediatric severe asthma suggested doses between 50 and 75 mg/kg to achieve concentrations within the hypothesized target range between 25 and 40 mg/L (Rower 2017).

Oral inhalation: Severe exacerbation: Limited data available: Children ≥2 years and Adolescents: Nebulized 150 mg isotonic magnesium sulfate mixed with albuterol and ipratropium every 20 minutes for 3 doses in the first hour of treatment to patients with severe acute asthma who did not respond to standard inhalation treatment (GINA 2020; Powell 2013). In a large randomized, placebo-controlled trial (n=508, including 252 who received magnesium sulfate treatment; ages: 2 to 16 years) improvement was statistically significant, but clinically significant changes were only observed in the most severe patients (SaO2 <92% with symptoms lasting <6 hours) (Powell 2013).

Dosing: Obesity

Refer to indication-specific dosing for obesity-related information (may not be available for all indications).

Reconstitution

IV: Dilute to ≤20% in a compatible solution (eg, D5W, NS) for IV infusion.

IM: A 25% or 50% concentration may be used.

Oral: Dissolve granules in 8 ounces of water prior to administration. May add lemon juice to improve taste.

Topical: Dissolve 2 cups of granules per gallon of warm water to use as a soaking aid.

Administration

Injection: May be administered IM, IO, or IV.

IM: Adults: 25% or 50% concentration.

Eclampsia/preeclampsia: May mix with lidocaine 2% to reduce injection pain (ACOG 202 2019).

IV, IO: Must be diluted to a ≤20% solution for IV infusion and may be administered IV push, IVPB, as a continuous IV infusion, or intraosseous (IO). When giving IV push, must dilute first and should generally not be given any faster than 150 mg/minute; may administer as an IV or IO bolus in patients with persistent pulseless VT or VF with known hypomagnesemia or with QT prolongation (torsades de pointes) (ACLS [Neumar 2010]). In patients with polymorphic VT (with pulse) associated with QT prolongation (torsades de pointes), administer IV over 15 minutes (range: 5 to 60 minutes) (ACLS [Neumar 2010]; AHA [Hazinski 2015]). In patients not in cardiac arrest, hypotension and asystole may occur with rapid administration. In patients with asthma (acute severe exacerbation), may administer single dose over 20 minutes to 60 minutes (GINA 2020; NAEPP 2007).

Maximal rate of infusion (routine administration for hypomagnesemia prevention/treatment): Up to 50% of an IV dose may be eliminated in the urine, therefore, slower administration may improve retention (maximum rate: 1 g/hour in asymptomatic hypomagnesemia). For doses <6 g, infuse over 8 to 12 hours and for larger doses infuse over 24 hours if patient is asymptomatic. If patient is severely symptomatic (or has conditions such as preeclampsia or eclampsia) more aggressive therapy (≤4 g over 4 to 5 minutes) may be required; patients should be closely monitored (Kraft 2005).

Oral: When used as a laxative, dissolve dose in 8 ounces of water prior to ingesting. Lemon juice may be added to the solution to improve the taste.

Topical: May dissolve granules to prepare a solution for use as a soaking aid or as a compress. To make a compress, use a towel to apply as a wet dressing.

Dietary Considerations

Whole grains, legumes and dark-green leafy vegetables are dietary sources of magnesium (IOM 1997).

Adequate intake (AI) (elemental magnesium) (IOM 1997):

1 to 6 months: 30 mg daily

7 to 12 months: 75 mg daily

Dietary recommended daily allowance (RDA) (elemental magnesium) (IOM 1997):

1 to 3 years: 80 mg daily

4 to 8 years: 130 mg daily

9 to 13 years: 240 mg daily

14 to 18 years:

Females: 360 mg daily

Pregnancy: 400 mg daily

Lactation: 360 mg daily

Males: 410 mg daily

19 to 30 years:

Females: 310 mg daily

Pregnancy: 350 mg daily

Lactation: 310 mg daily

Males: 400 mg daily

≥31 years:

Females: 320 mg daily

Pregnancy: 360 mg daily

Lactation: 320 mg daily

Males: 420 mg daily

Storage

Prior to use, store at room temperature of 20°C to 25°C (68°F to 77°F). Do not freeze. Refrigeration of solution may result in precipitation or crystallization.

Drug Interactions

Alfacalcidol: May increase the serum concentration of Magnesium Salts. Management: Consider using a non-magnesium-containing antacid or phosphate-binding product in patients also receiving alfacalcidol. If magnesium-containing products must be used with alfacalcidol, serum magnesium concentrations should be monitored closely. 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. Management: Separate administration of alpha-lipoic acid from that of any magnesium-containing compounds by several hours. If alpha-lipoic acid is given 30 minutes before breakfast, then administer oral magnesium-containing products at lunch or dinner. Consider therapy modification

Baloxavir Marboxil: Polyvalent Cation Containing Products may decrease the serum concentration of Baloxavir Marboxil. Avoid combination

Bictegravir: Polyvalent Cation Containing Products may decrease the serum concentration of Bictegravir. Management: Administer bictegravir under fasting conditions at least 2 hours before or 6 hours after polyvalent cation containing products. Coadministration of bictegravir with or 2 hours after most polyvalent cation products is not recommended. Consider therapy modification

Bisphosphonate Derivatives: Polyvalent Cation Containing Products may decrease the serum concentration of Bisphosphonate Derivatives. Management: Avoid administration of oral medications containing polyvalent cations 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

CNS Depressants: Magnesium Sulfate may enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Deferiprone: Polyvalent Cation Containing Products 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. Administer the dolutegravir/rilpivirine combination product at least 4 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: Polyvalent Cation Containing Products may decrease the serum concentration of Eltrombopag. Management: Administer eltrombopag at least 2 hours before or 4 hours after oral administration of any polyvalent cation containing product. Consider therapy modification

Elvitegravir: Polyvalent Cation Containing Products may decrease the serum concentration of Elvitegravir. Management: Administer elvitegravir 2 hours before or 6 hours after the administration of polyvalent cation containing products. 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 use of a magnesium-containing antacid. 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

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

PenicillAMINE: Polyvalent Cation Containing Products may decrease the serum concentration of PenicillAMINE. Management: Separate the administration of penicillamine and oral polyvalent cation containing products by at least 1 hour. Consider therapy modification

Phosphate Supplements: Magnesium Salts may decrease the serum concentration of Phosphate Supplements. Management: Administer oral phosphate supplements as far apart from the administration of an oral magnesium salt as possible to minimize the significance of this interaction. Exceptions: Sodium Glycerophosphate Pentahydrate. Consider therapy modification

Quinolones: Magnesium Salts may decrease the serum concentration of Quinolones. Management: Administer oral quinolones several hours before (4 h for moxi/pe/spar/enox-, 2 h for others) or after (8 h for moxi-, 6 h for cipro/dela-, 4 h for lome/pe/enox-, 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

Ritodrine: May enhance the adverse/toxic effect of Magnesium Sulfate. Monitor therapy

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

Tetracyclines: Magnesium Salts may decrease the absorption of Tetracyclines. Only applicable to oral preparations of each agent. Management: Avoid coadministration of oral magnesium salts and oral tetracyclines. If coadministration cannot be avoided, administer oral magnesium at least 2 hours before, or 4 hours after, oral tetracyclines. Monitor for decreased tetracycline therapeutic effects. Exceptions: Eravacycline; Tigecycline. Consider therapy modification

Trientine: Polyvalent Cation Containing Products may decrease the serum concentration of Trientine. Management: Avoid concomitant administration of trientine and oral products that contain polyvalent cations. If oral iron supplements are required, separate the administration by 2 hours. If other oral polyvalent cations are needed, separate administration by 1 hour. Consider therapy modification

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 (IV; dose related), hypotension (IV; rate related), vasodilation (IV; rate related)

Endocrine & metabolic: Hypermagnesemia

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 2005) are recommended to avoid potential for errors resulting in toxicity. Monitor mother and fetus closely. Use longer than 5 to 7 days may cause adverse fetal events.

Dosage form specific issues:

• Aluminum: The parenteral product may contain aluminum; toxic aluminum concentrations may be seen with high doses, prolonged use, or renal dysfunction. Premature neonates are at higher risk due to immature renal function and aluminum intake from other parenteral sources. Parenteral aluminum exposure of >4 to 5 mcg/kg/day is associated with CNS and bone toxicity; tissue loading may occur at lower doses (Federal Register 2002). See manufacturer's labeling.

Other warnings/precautions:

• Appropriate use: Unlikely to effectively terminate irregular/polymorphic VT (with normal baseline QT interval) (AHA [Neumar 2010]).

• 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: Magnesium toxicity can lead to fatal cardiovascular arrest and/or respiratory paralysis.

• Self-medication (OTC Use): When used as a soaking aid, patients should not use if there is evidence of infection or prompt relief is not obtained. When used as a laxative, patients should consult a health care provider prior to use if they have: kidney disease; are on a magnesium-restricted diet; have abdominal pain, nausea, or vomiting; change in bowel habits lasting >2 weeks; have already used a laxative for >1 week.

Monitoring Parameters

IV: 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; renal function.

Obstetrics: Patient status including vital signs, oxygen saturation, respiration, deep tendon reflexes, level of consciousness, fetal heart rate, maternal uterine activity, renal function. Monitor magnesium concentrations every 4 hours in patients with renal dysfunction (every 2 hours if serum magnesium is >8 mEq/L (ACOG 2020).

Pregnancy Considerations

Magnesium crosses the placenta; serum concentrations in the fetus are similar to those in the mother (Idama 1998; Osada 2002). Continuous maternal use for >5 to 7 days (in doses such as those used for preterm labor, an off-label use) may cause fetal hypocalcemia and bone abnormalities, as well as fractures in the neonate.

Magnesium sulfate injection is used for the prevention and treatment of seizures in pregnant or postpartum women with severe preeclampsia or eclampsia (ACOG 2020). Magnesium sulfate may also be used prior to early preterm delivery for neuroprotection to reduce the risk of cerebral palsy (ACOG 2010; Reeves 2011); treatment may be of benefit when birth is anticipated before 32 weeks' gestation (ACOG 2016). Tocolytics may be used for the short-term (48 hour) prolongation of pregnancy to allow for the administration of antenatal steroids and should not be used prior to fetal viability or when the risks of use to the fetus or mother are greater than the risk of preterm birth; maintenance therapy with tocolytics is ineffective and not recommended. Magnesium sulfate can be used up to 48 hours in women at risk of delivery within 7 days; however, it is not the preferred tocolytic (ACOG 2016). Magnesium sulfate injection may be used in conjunction with other tocolytics for neuroprotection; however, an increased risk of maternal complications may be observed when used in combination with some tocolytic agents (ACOG 2016).

Patient Education

What is this drug used for?

Injection:

• It is used to treat or prevent low magnesium levels.

• It is used to prevent and control seizures during pregnancy.

Granules used by mouth:

• It is used to treat constipation.

Granules used as soaks:

• It is used to treat minor sprains or bruises.

All products:

• It may be given to you for other reasons. Talk with the doctor.

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• High magnesium levels like confusion, feeling sluggish, slow movements, shortness of breath, nausea, severe dizziness, or passing out.

• Low calcium like muscle cramps or spasms, numbness and tingling, or seizures.

• Abnormal heartbeat

• Sensation of cold

• Sweating a lot

• Flushing

• Trouble moving

• Severe diarrhea

• Severe nausea

• Severe vomiting

• Black, tarry, or bloody stools

• Cramps

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a limited summary of general information about the medicine’s uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

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