Magnesium Sulfate Dosage
Medically reviewed by Drugs.com. Last updated on Jun 12, 2024.
Applies to the following strengths: 50%; 10 mg/mL-D5%; 20 mg/mL-D5%; 40 mg/mL-D5%; 80 mg/mL-D5%; 125 mg/mL; 10 g/1000 mL; 40 mg/mL; 80 mg/mL; 100 mg/mL; 2 g/50 mL-sterile water; 4 g/50 mL-sterile water; 4 g/100 mL-sterile water; 20 g/500mL-sterile water; 40 g/1000 mL-sterile water; 1 g/50 mL-D5%; 2 g/50 mL-D5%; 6 g/50 mL-D5%; 4 g/100 mL-NaCl 0.9%; 1 g/50 mL-NaCl 0.9%; 1 g/100 mL-NaCl 0.9%; 2 g/50 mL-NaCl 0.9%; 6 g/50 mL-NaCl 0.9%; 3 g added to NaCl 0.9% 50 mL; 6 g added to NaCl 0.9% 100 mL; 2 g added to D5% 50 mL; 4 g added to D5% 100 mL; 50 g added to LR 500 mL; 20 g added to LR 500 mL; 10 g added to D5% 250 mL; 3 g added to D5% 100 mL; 40 mg/mL-LR; 80 mg/mL-LR; 120 mg/mL-D5%; 83 mg/mL-D5%; 83 mg/mL-LR; 1000 mg/ 50 mL-NaCl 0.9%; 2 g/100 mL-NaCl 0.9%; 2 g/100 mL-D5%; 6 g/100 mL-D5%
Usual Adult Dose for:
- Hypomagnesemia
- Atrial Tachycardia
- Pre-eclampsia/Eclampsia
- Constipation
- Barium Poisoning
- Seizures
- Cerebral Edema
Usual Pediatric Dose for:
Additional dosage information:
Usual Adult Dose for Hypomagnesemia
1 gram IM every 6 hours for 4 doses (mild hypomagnesemia) or as much as 250 mg/kg IM within a 4-hour period (severe hypomagnesemia)
OR
5 grams in 1 liter of appropriate diluent IV over 3 hours
- Do not exceed IV infusion rate of 150 mg/minute
Comments:
- Appropriate diluents include 5% dextrose or 0.9% sodium chloride.
- Use caution to prevent exceeding renal excretory capacity.
- May be given undiluted intramuscularly.
- Carefully adjust dosage to individual requirements and response.
- Discontinue as soon as the desired effect is obtained.
Usual Adult Dose for Atrial Tachycardia
3 to 4 grams (30 to 40 mL of a 10% solution) IV over 30 seconds
Comments:
- Use with EXTREME CAUTION.
- Use only if simpler methods have failed and there is no evidence of myocardial damage.
Use: Paroxysmal atrial tachycardia
Usual Adult Dose for Pre-eclampsia/Eclampsia
Severe pre-eclampsia or eclampsia:
Initial dose: 4 to 5 grams IV in 250 mL of appropriate diluent, with simultaneous IM administration of up to 5 grams (10 mL undiluted solution) in EACH buttock; total dose: 10 to 14 grams
- Initial IV dose of 4 grams may also be diluted to a 10% or 20% solution and injected IV over 3 to 4 minutes
Maintenance dose: 4 to 5 grams IM into alternate buttocks every 4 hours as needed
OR
Maintenance dose: 1 to 2 grams/hour IV by constant infusion
- Continue therapy until paroxysms cease
Comments:
- Appropriate diluents include 5% dextrose or 0.9% sodium chloride.
- A serum magnesium level of 6 mg/100 mL is considered optimal for seizure control.
- The need to continue therapy is based on the continuing presence of patellar reflex and adequate respiratory function.
- Continuous maternal administration beyond 5 to 7 days can cause fetal abnormalities.
- Monitor serum magnesium and patient clinical status to avoid overdosage.
- Clinical indications of a safe dose include presence of patellar reflex (knee jerk) and absence of respiratory depression (about 16 breaths/minute or more).
- Test patellar reflex before repeat doses and do not administer magnesium if absent.
- Deep tendon reflexes begin to diminish at magnesium levels above 4 mEq/L.
- Reflexes may be absent at 10 mEq/L, where there is potential for respiratory paralysis.
- An injectable calcium salt should be immediately available to counteract magnesium intoxication.
Uses: Prevention and control of seizures in pre-eclampsia and eclampsia
Usual Adult Dose for Constipation
2 to 4 level teaspoons dissolved in 8 ounces water orally
- Repeat dose in 4 hours if needed.
Uses: Cathartic or laxative
Usual Adult Dose for Barium Poisoning
1 to 2 grams IV
- Do not exceed IV infusion rate of 150 mg/minute
Use: To counteract the muscle-stimulating effects of barium poisoning
Usual Adult Dose for Seizures
1 gram intramuscularly or IV
- Do not exceed IV infusion rate of 150 mg/minute
Use: Seizures associated with epilepsy, glomerulonephritis, or hypothyroidism
Usual Adult Dose for Cerebral Edema
2.5 grams (25 mL of a 10% solution) IV
- Do not exceed IV infusion rate of 150 mg/minute
Use: Reduction of cerebral edema
Usual Pediatric Dose for Constipation
Epsom Salt:
12 years and older: 2 to 4 level teaspoons dissolved in 8 ounces water orally
6 to 11 years: 1 to 2 level teaspoons dissolved in 8 ounces of water orally
Under 6 years: Not recommended
Maximum dose: 2 doses per day
Comments:
- Repeat dose in 4 hours if needed.
- Generally produces a bowel movement in 30 minutes to 6 hours.
Uses: Cathartic or laxative
Renal Dose Adjustments
Use with caution.
- Magnesium is removed from the body solely by the kidneys.
- Parenteral use in renal insufficiency may lead to magnesium intoxication.
- Urine output should be maintained at 100 mL or more during the 4 hours preceding each dose.
- Monitoring serum magnesium and patient clinical status is essential to avoid overdose in toxemia of pregnancy.
- Reserve IV use for immediate control of life-threatening convulsions.
Prevention/Control of pre-eclamptic and eclamptic seizures:
- Maximum dosage is 20 grams/48 hours for severe renal insufficiency.
- Obtain serum magnesium concentrations frequently.
- Continuous maternal administration beyond 5 to 7 days can cause fetal abnormalities.
Liver Dose Adjustments
No adjustment recommended.
Dialysis
Data not available
Other Comments
Administration advice:
- Solutions for IV administration must be diluted to a concentration of 20% or less.
- Deep intramuscular administration of the undiluted parenteral solution is appropriate for adults.
- Dilute the parenteral solution to a concentration of 20% or less for IM administration to children.
IV compatibility:
- Compatible with 5% dextrose and 0.9% sodium chloride solutions
- The manufacturer product information should be consulted for a list of incompatible substances.
Monitoring:
- Monitor serum magnesium and patient clinical status to avoid overdosage in toxemia of pregnancy.
- Clinical indications of a safe dose include presence of patellar reflex (knee jerk) and absence of respiratory depression (about 16 breaths/minute or more).
- Test patellar reflex before repeat doses and do not administer magnesium if absent.
- Deep tendon reflexes begin to diminish at magnesium levels above 4 mEq/L.
- Reflexes may be absent at 10 mEq/L, where there is potential for respiratory paralysis.
- Serum magnesium levels of 3 to 6 mg/100 mL (2.5 to 5 mEq/L) are usually sufficient to control convulsions.
- An injectable calcium salt should be immediately available to counteract magnesium intoxication in toxemia of pregnancy.
Frequently asked questions
- When is the best time to take magnesium, morning or night?
- Should I take magnesium with or without food?
- Does magnesium help with restless leg syndrome (RLS)?
- Does magnesium help with headaches and migraines?
- Does magnesium help with weight loss?
More about magnesium sulfate
- Check interactions
- Compare alternatives
- Pricing & coupons
- Reviews (6)
- Side effects
- During pregnancy
- Drug class: laxatives
- Breastfeeding
Patient resources
- Magnesium sulfate drug information
- Magnesium sulfate injection
- Magnesium Sulfate Granules (Epsom Salt)
Other brands
Professional resources
- Magnesium Sulfate monograph
- Magnesium (FDA)
- Magnesium Sulfate (FDA)
- Magnesium Sulfate in Dextrose Injection (FDA)
- Magnesium Water (FDA)
Related treatment guides
Further information
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
