Medically reviewed on Sep 20, 2017
What is MST?
MST is a salicylate (sa-LIS-il-ate). It works by reducing substances in the body that cause pain, fever, and inflammation.
MST is used to treat mild-to-moderate pain, fever, inflammatory conditions, and pain, swelling, or stiffness associated with arthritis.
MST may also be used for purposes not listed in this medication guide.
Do not take more of MST than recommended on the label. An overdose of magnesium salicylate can be fatal.
MST may cause stomach or intestinal bleeding, which can be fatal. These conditions can occur without warning while you are using this medicine, especially in older adults.
Do not give this medicine to a child or teenager with a fever, flu symptoms, or chicken pox. Salicylates can cause Reye's syndrome, a serious and sometimes fatal condition in children.
Before taking this medicine
You should not use MST if you are allergic to it, or if you have ever had:
a severe allergic reaction after taking aspirin or an NSAID (non-steroidal anti-inflammatory drug) such as Advil, Motrin, Aleve, Orudis, Indocin, Lodine, Voltaren, Toradol, Mobic, Relafen, Feldene, and others.
Do not give this medicine to a child or teenager with a fever, flu symptoms, or chicken pox. MST can cause Reye's syndrome, a serious and sometimes fatal condition in children. This medicine is not approved for use by anyone younger than 12 years old.
To make sure MST is safe for you, tell your doctor if you have ever had:
stomach ulcer or bleeding;
heart disease, high blood pressure; or
Taking MST during late pregnancy may cause bleeding in the mother or the baby during delivery. Tell your doctor if you are pregnant or plan to become pregnant.
Magnesium salicylate can pass into breast milk and may harm a nursing baby. You should not breast-feed while using this medicine.
How should I take MST?
Use exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.
Take MST with a full glass of water.
Take with food if MST upsets your stomach.
If you need surgery, tell the surgeon ahead of time that you are using MST. You may need to stop using the medicine for a short time.
Call your doctor if your symptoms do not improve, or if you have a fever lasting longer than 3 days or pain lasting longer than 10 days.
Store at room temperature away from moisture and heat.
What happens if I miss a dose?
Since MST is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of magnesium salicylate can be fatal.
What should I avoid while taking MST?
Avoid drinking alcohol while you are taking MST. Alcohol may increase your risk of stomach bleeding.
Ask a doctor or pharmacist before using any cold, allergy, or pain medication. Many medicines available over the counter contain aspirin or other medicines similar to MST. Taking certain products together can cause you to get too much of this type of medication. Check the label to see if a medicine contains aspirin, ibuprofen, ketoprofen, or naproxen.
MST side effects
Get emergency medical help if you have signs of an allergic reaction: hives; pale or clammy skin; rapid heartbeats; dilated pupils; unexplained weakness or dizziness; fainting; difficult breathing, wheezing; swelling of your face, lips, tongue, or throat.
Stop using MST and call your doctor at once if you have:
redness or swelling;
ringing in your ears, hearing loss;
behavior changes with nausea and vomiting in a child using MST;
worsening fever or pain; or
signs of stomach bleeding--feeling light-headed, ongoing stomach pain, bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds.
Side effects may be more likely in older adults.
Common side effects may include:
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What other drugs will affect MST?
Ask a doctor or pharmacist if it is safe for you to use MST if you are also using:
insulin or oral diabetes medicine;
a steroid medicine;
This list is not complete. Other drugs may interact with magnesium salicylate, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
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