Generic name: magnesium sulfate [ mag-NEE-zee-um-SUL-fate ]
Brand names: Epsal, Epsom Salt, Rite Aid First Aid Epsom Salt
Drug classes: Laxatives, Minerals and electrolytes, Miscellaneous anticonvulsants

Medically reviewed by Drugs.com. Last updated on Oct 24, 2023.

Uses for magnesium sulfate

Magnesium sulfate is used for short-term relief of constipation. It is also used as a soaking solution to relieve minor sprains, bruises, muscle aches or discomfort, joint stiffness or soreness, and tired feet. This medicine is a laxative and soaking solution.

This medicine is available without a prescription.

Before using magnesium sulfate

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of magnesium sulfate to relieve constipation in children 6 years of age or older. However, safety and efficacy have not been established in children younger than 6 years of age.

Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of magnesium sulfate as a soaking solution in children.

Geriatric

No information is available on the relationship of age to the effects of magnesium sulfate in geriatric patients.

Interactions with Medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.

Related/similar drugs

clonazepam, lamotrigine, topiramate, diazepam, Lamictal, Klonopin, sotalol

Proper use of magnesium sulfate

Use this medicine only as directed by your doctor. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered.

If you are using this medicine without a prescription, follow the instructions on the package.

Use as a laxative:

• Dissolve the powder in 8 ounces (oz) of water.
• Add lemon juice to the mixture to improve the taste.
• Drink the mixture at least 2 hours before or after other medicines.

Use as a soaking solution:

• Dissolve the powder in warm water for use as a compress, soaking solution, or bath.
• As a compress, apply with a bandage or towel for 30 minutes up to 3 times per day.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For oral dosage form (powder for solution):
  • For constipation:
    • Adults and children 12 years of age and older—2 to 6 level teaspoons per day as a single dose or in 2 divided doses. Dissolve the powder in 8 ounces (oz) of water. If the dose is divided, separate the doses by at least 4 hours. Do not use more than 2 doses per day.
    • Children 6 to 11 years of age—1 to 2 level teaspoons per day as a single dose or in 2 divided doses. Dissolve the powder in 8 ounces (oz) of water. If the dose is divided, separate the doses by at least 4 hours. Do not use more than 2 doses per day.
    • Children younger than 6 years of age—Use is not recommended.
• For topical dosage form (powder for solution):
  • For minor sprains, bruises, muscle or joint discomfort, tired feet:
    • Adults—2 cups dissolved in one gallon of warm water.
    • Children—Use and dose must be determined by your doctor.

Storage

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

If the powder has settled and formed a thick layer, gently tap the carton to free the granules.

Precautions while using magnesium sulfate

If your symptoms do not improve within a few days or if they become worse, check with your doctor.

Laxative use: Before using this medicine, talk to your doctor first

• If you are pregnant or breastfeeding.
• If you noticed a sudden change in bowel habits that continued for more than 2 weeks.
• If you have stomach pain, nausea, or vomiting.
• If you are on a magnesium-restricted diet.
• If you have already used a laxative for longer than a week.

Laxative use: Stop using this medicine and check with your doctor if you have rectal bleeding or do not have a bowel movement after use.

Soaking solution use: Do not use this medicine if you are pregnant or have diabetes, unless your doctor tells you otherwise.

Soaking solution use: Stop using this medicine and check with your doctor if you have a skin irritation or infection.

Side Effects of magnesium sulfate

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Incidence not known

• Confusion
• dizziness or lightheadedness
• fast, slow, or irregular heartbeat
• low blood pressure
• muscle weakness
• skin infection after soaking
• sleepiness

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

• Diarrhea
• skin irritation after soaking

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Commonly used brand name(s)

In the U.S.

• Epsal
• Epsom Salt
• Rite Aid First Aid Epsom Salt

In Canada

• Mag 2
• Magnesium-Rougier

Available Dosage Forms:

• Powder
• Powder for Solution
• Powder for Suspension
• Crystal
• Foam
• Spray

Therapeutic Class: Laxative

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer