Magnesium Sulfate
Pronunciation: (mag-NEE-zee-um SUL-fate).
- Generic name
- Magnesium sulfate
- Brand names
- Mag-Ox Sulfate, Magnesol, Epsom Salt, Magnetol, Magnasulf, Magnesium Sulphate Injection IP
- Drug class
- Electrolyte supplement; Anticonvulsant; Tocolytic
Availability and supply rules vary by country
Trade names by country: United States
Australia: · Full directory
What Magnesium sulfate is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how Magnesium sulfate works
Magnesium sulfate acts as a physiological calcium antagonist, blocking neuromuscular transmission and decreasing the release of acetylcholine at the motor end plate. It stabilizes excitable membranes and reduces the risk of seizures in eclampsia. As an electrolyte, it replenishes magnesium stores and is essential for enzymatic reactions, muscle contraction, and nerve function. (1)
What Magnesium sulfate is used for
Treatment and prevention of low blood magnesium (hypomagnesemia)
Treatment and prevention of low blood magnesium (hypomagnesemia) (2) (3)
Prevention and control of seizures in severe preeclampsia and eclampsia during pregnancy
Prevention and control of seizures in severe preeclampsia and eclampsia during pregnancy (2) (3)
Tocolytic use to delay preterm labor
The FDA has warned that continuous IV use beyond 5-7 days for this specific tocolytic purpose can cause fetal bone problems — see Pregnancy section. (2) (3)
Short-term laxative for constipation (oral Epsom salt)
Short-term laxative for constipation (oral Epsom salt) (2) (3)
Certain arrhythmias
Before taking Magnesium sulfate
Do not take / not appropriate for
- heart block, severe renal impairment, myasthenia gravis, and hypersensitivity to magnesium sulfate. (Contraindication) (2)
Tell your clinician about
(2) (3)How to take Magnesium sulfate
- General Instructions: Take magnesium sulfate exactly as prescribed. For injection, it is administered by a healthcare professional. For oral use (as Epsom salt), dissolve the recommended dose in water and drink. Do not exceed the recommended dose.. Adult Dosing: For hypomagnesemia: 1-2 g IV over 1 hour, repeated as needed. For eclampsia: 4-6 g IV loading dose, then 1-2 g/hour infusion. For constipation (oral): 2-4 teaspoons (10-20 g) dissolved in water, as a single dose.. Pediatric Dosing: Dosing is weight-based and determined by a healthcare provider. Do not give to children without medical supervision.. Administration: Injectable forms are given IV or IM by healthcare professionals. Oral forms should be dissolved in water and taken by mouth. Do not inject oral preparations.. When To Stop: Contact your doctor promptly if you experience serious side effects or if your symptoms resolve — let the clinician you see advise on whether to continue or stop treatment. Do not use for longer than directed.. Storage: Store at room temperature away from moisture and heat. Keep out of reach of children.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2) (3)
Missed dose
Injectable magnesium sulfate is scheduled and given by your healthcare team, so if a dose or infusion is missed, they will manage the timing. For the oral (Epsom salt) laxative form used for occasional constipation, do not take an extra dose to make up for one that was missed — let the clinician or pharmacist you see advise on timing if you have questions.
Overdose
Overdose can cause serious symptoms such as severe drowsiness, loss of reflexes, difficulty breathing, or cardiac arrest. Seek emergency medical help immediately if overdose is suspected. (2) (3)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Flushing, sweating
Incidence: Reported in the clinician-authored database; frequency not established
Low blood pressure (hypotension)
Incidence: Reported in the clinician-authored database; frequency not established
Drowsiness
Incidence: Reported in the clinician-authored database; frequency not established
Muscle weakness, depressed reflexes
Incidence: Reported in the clinician-authored database; frequency not established
Loss of deep tendon reflexes, severe drowsiness, difficulty breathing, or irregular heartbeat — these can be signs of magnesium toxicity and warrant urgent medical attention.
(1)Serious warnings
Use with caution in patients with impaired kidney function — serious
Symptoms: Use with caution in patients with impaired kidney function. Monitor for signs of magnesium toxicity, especially with IV use. May interact with certain medications, including neuromuscular blockers and CNS depressants. Not recommended for routine use in pregnancy except for specific indications (e.g., preeclampsia/eclampsia). Prolonged use can lead to electrolyte imbalances.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2) (3)
Contraindications recorded in the clinician database — serious
Symptoms: Contraindications recorded in the clinician database: Contraindications include heart block, severe renal impairment, myasthenia gravis, and hypersensitivity to magnesium sulfate. Use with caution in patients with mild to moderate renal dysfunction, neuromuscular diseases, or those receiving CNS depressants. Monitor closely in pregnancy and lactation.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2) (3)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Recorded interactions | Magnesium sulfate can interact with certain antibiotics (such as tetracyclines and quinolones), muscle relaxants, CNS depressants, and other medications that affect electrolyte balance. It may increase the effects of neuromuscular blocking agents and potentiate CNS depression. Always inform your healthcare provider about all medications and supplements you are taking. | (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Magnesium sulfate is widely used in pregnancy under close medical supervision to prevent and control seizures in severe preeclampsia/eclampsia — this short, monitored use is standard obstetric practice. Separately, the FDA has warned that continuous IV use for more than 5-7 days to delay preterm labor (a tocolytic use) can cause fetal hypocalcemia and bone problems (skeletal demineralization, osteopenia, and reported neonatal fractures); the shortest duration that can cause harm is not known. It should be used in pregnancy only if clearly needed, and any use beyond 5-7 days should be discussed with the treating clinician. (2) (3)
Breastfeeding
Discuss with a healthcare provider before use while breastfeeding. (2) (3)
Children
Frequency: Not recommended for pediatric use.. Weight Based: Not established for pediatric use; dosing is typically based on clinical judgment.. Max Daily Dose: Not recommended for pediatric use.. Max Single Dose: Not recommended for pediatric use.. Age Restrictions: Safety not established in children. (2) (3)
Renal_impairment
In severe renal insufficiency, the maximum recommended dosage is 20 g per 48 hours, with frequent monitoring of blood magnesium levels, per FDA-approved labeling. Use with caution in mild-to-moderate renal impairment; magnesium is cleared by the kidneys and toxicity risk rises as kidney function falls. (2) (3)
Hepatic_impairment
In severe renal insufficiency, the maximum recommended dosage is 20 g per 48 hours, with frequent monitoring of blood magnesium levels, per FDA-approved labeling. Use with caution in mild-to-moderate renal impairment; magnesium is cleared by the kidneys and toxicity risk rises as kidney function falls. (2) (3)
Monitoring
(2) (3)Storage
Per the clinician-authored record: store at room temperature away from moisture and heat, and keep out of reach of children. This general instruction has not been independently confirmed against a specific product's current label in this research pass, so always follow the storage instructions printed on your own product's packaging.
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General — commonly used obstetric (ACOG-aligned) protocol
Indication: Eclampsia / severe preeclampsia (seizure prevention)
Dose summary: Loading dose 4-6 g IV over 15-30 minutes, followed by a maintenance dose of 1-2 g/hour IV.
Renal context: In severe renal insufficiency, FDA labeling caps total dosage at 20 g per 48 hours with frequent serum magnesium monitoring; use lower maintenance doses and monitor closely in mild-to-moderate renal impairment. (1)
General — FDA package-insert historical protocol
Indication: Eclampsia / severe preeclampsia (seizure prevention)
Dose summary: Initial loading dose totaling 10-14 g (IV 4-5 g in 250 mL diluent, or 4 g concentrated over 3-4 minutes, combined with IM up to 10 g split between buttocks); maintenance 4-5 g IM every 4 hours or 1-2 g/hour continuous IV infusion; maximum 30-40 g in 24 hours.
Renal context: In severe renal insufficiency, maximum dosage is 20 g per 48 hours, with frequent serum magnesium monitoring. (2)
General
Indication: Hypomagnesemia (magnesium replacement)
Dose summary: Mild deficiency: 1 g (2 mL of 50% solution) IM every 6 hours for 4 doses. Severe hypomagnesemia: up to 250 mg/kg IM within 4 hours, or 5 g in 1 L diluent by slow IV infusion over 3 hours.
Renal context: In severe renal insufficiency, maximum dosage is 20 g per 48 hours, with frequent serum magnesium monitoring. (2)
Frequently asked questions
What is magnesium sulfate used for?
Magnesium sulfate is used to treat low magnesium levels, control seizures in pregnancy (eclampsia), delay preterm labor, and as a laxative for constipation. It is also used in some heart rhythm disorders.
How is magnesium sulfate given?
It can be given by injection (IV or IM) in a hospital setting or taken orally as Epsom salts for constipation. Injectable forms are only administered by healthcare professionals.
What are the signs of magnesium sulfate overdose?
Symptoms include severe drowsiness, loss of deep tendon reflexes, difficulty breathing, irregular heartbeat, and cardiac arrest. Seek emergency help if overdose is suspected.
Can I use magnesium sulfate during pregnancy?
Magnesium sulfate is commonly used in pregnancy to prevent and treat seizures in preeclampsia/eclampsia, but should only be used under medical supervision for specific indications.
Are there any foods or drugs I should avoid while taking magnesium sulfate?
Avoid other magnesium-containing supplements and certain antibiotics (like tetracyclines and quinolones) unless advised by your doctor. Inform your healthcare provider about all medications you are taking.
What should I do if I miss a dose?
Injectable doses are scheduled and given by your healthcare team, who will manage timing if one is missed. For the oral laxative form, do not take an extra dose to catch up — check with your pharmacist or clinician if you have questions.
Is magnesium sulfate safe for children?
Magnesium sulfate may be used in children for specific medical reasons, but dosing must be determined by a healthcare provider. Do not give to children without medical advice.
What happens if I take too much Magnesium sulfate?
Taking too much Magnesium sulfate can lead to magnesium toxicity, characterized by symptoms like flushing, sweating, hypotension, depressed reflexes, muscle weakness, and respiratory depression. In severe cases, it can cause cardiac arrest. If you suspect an overdose, seek immediate emergency medical attention. Prompt intervention is crucial to manage these potentially life-threatening effects.
Can I drink alcohol while taking Magnesium sulfate?
It is generally advisable to avoid or limit alcohol consumption while taking Magnesium sulfate. Alcohol can exacerbate some of the central nervous system depressant effects of Magnesium sulfate, potentially leading to increased drowsiness, dizziness, and impaired coordination. Additionally, alcohol can affect electrolyte balance, which may interfere with the therapeutic effects of Magnesium sulfate. Always consult your healthcare provider for personalized advice.
Is Magnesium sulfate safe during pregnancy?
Magnesium sulfate is categorized as a Pregnancy Category D medication, meaning there is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk in certain situations. It is commonly used in obstetrics for conditions like pre-eclampsia and eclampsia. However, its use should always be under the direct supervision and guidance of a healthcare provider who can weigh the potential benefits against the risks for both the mother and the fetus.
What is the mechanism of action of Magnesium sulfate?
Magnesium sulfate acts as a physiological calcium antagonist, blocking neuromuscular transmission and decreasing the release of acetylcholine at the motor end plate. It stabilizes excitable membranes and reduces the risk of seizures in eclampsia. As an electrolyte, it replenishes magnesium stores and is essential for enzymatic reactions, muscle contraction, and nerve function. (1)
What is the generic name of Magnesium Sulfate?
The generic name is Magnesium sulfate. It is sold under brand names including Mag-Ox Sulfate, Magnesol, Epsom Salt, Magnetol, Magnasulf, Magnesium Sulphate Injection IP.
What class of drug is Magnesium sulfate?
Magnesium Sulfate is classed as: Electrolyte supplement; Anticonvulsant; Tocolytic.
References
- Magnesium sulfate — MedGuideGlobal medicine recordMedGuideGlobal internal clinician-authored medicine record · Global (internal) · accessed 2026-08-06 · source 1
- Magnesium Sulfate Injection, USP 50% — prescribing informationU.S. Food and Drug Administration / DailyMed · United States · accessed 2026-08-06 · source 2
- FDA Drug Safety Communication: FDA Recommends Against Prolonged Use of Magnesium Sulfate to Stop Pre-term Labor Due to Bone Changes in Exposed BabiesU.S. Food and Drug Administration · United States · dated 2013 · accessed 2026-08-06 · source 3
- EPSOM SALT (MAGNESIUM SULFATE) GRANULE, FOR SOLUTION [SAFEWAY INC] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 4
- Acid Reducer — FDA approval record (Drugs@FDA ANDA212088)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 5
- Magnesium — RxNorm normalized drug concept (RXCUI 6574)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 6
Brand names by country
Single-ingredient Magnesium sulfate names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- The Vitamin ShoppeThe Vitamin Shoppe
- SolgarSolgar
- BluebonnetBluebonnet
- Douglas LaboratoriesDouglas Laboratories
- KirkmanKirkman
- NutriCologyNutriCology
- Integrative TherapeuticsIntegrative Therapeutics
- Source NaturalsSource Naturals
- Finest NutritionFinest Nutrition
- TumorXTumorX