Magnesium Sulfate Dosage
Medically reviewed by Drugs.com. Last updated on Aug 16, 2023.
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.
More about magnesium sulfate
- Check interactions
- Compare alternatives
- Pricing & coupons
- Reviews (5)
- Side effects
- During pregnancy
- Drug class: laxatives
- Breastfeeding
Patient resources
- Magnesium sulfate drug information
- Magnesium sulfate injection
- Magnesium sulfate (Advanced Reading)
- Magnesium Sulfate Granules (Epsom Salt)
Other brands
Professional resources
Related treatment guides
Further information
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
