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Epsom salt

Generic Name

milk of magnesia


Trade Name

Phillips Milk of Magnesia (Tablet,Liquid)
Epsom Salt
This product is available in an over-the-counter form.


What is milk of magnesia?

Milk of magnesia is a saline type laxative. This means that the magnesia acts to pull a salt or saline solution into the intestines from the blood. This excessive fluid then provides a flushing or laxative action within the intestines.


What is it used for?

This preparation is useful for the temporary relief of constipation. It can also be used for indigestion or heartburn, but the diarrhea side effect usually limits its use.


How do I take it?

Follow your physician’s instructions carefully. Shake the liquid well before using. Take this medication with a full glass of water or juice. Store it in a tightly sealed container. Keep all medications away from children. Never share your medications with anyone else.


What do I do for a missed dose?

This is usually not a problem since most people only take this when they have constipation. Because this medication is not recommended for chronic use, there is no medical benefit for doubling the dose. Doubling the dose may cause too harsh of a laxative effect.


Are there interactions with food or beverages?

There are no known interactions with food or beverages but an increase in liquids and a diet high in fiber can be helpful in alleviating constipation.


Are there interactions with other drugs?

An interaction generally means that one drug may increase or decrease the effect of another drug. Also, the more medications a person takes, the more likely there will be a drug interaction. Interactions with this drug may occur with tetracycline antibiotics such as Achromycin and Sumycin.


Is there a problem if I have another disorder or disease?

At times, a drug may have a different or enhanced effect when other diseases are present. At other times, the drug may worsen or effect another disease. When taken in occasional doses, there are generally no problems with any laxative or antacid. Taken this way, it is unlikely that you will get an excess of magnesium. However, patients with severe chronic kidney disease need to be careful not to get too much, as magnesium toxicity may occur.


What about allergies?

People who have known allergies or asthma may be at an increased risk for a reaction from any new medication. The physician should always know a patient’s allergy history. Signs of an allergic reaction are skin rash, hives and itching. Of course, a person should not take milk of magnesia if there has been a previous reaction to this or other laxatives.


What if I’m pregnant, considering pregnancy or breast-feeding?

Most females now know that, if possible, no drug, including alcohol, should be taken during pregnancy or lactation. The potential danger, of course, is an injury to the baby. However, some drugs are much safer than others in this regard. So, the FDA has a grading system for each drug which reflects what is known medically. It ranks drugs from A, where medical studies show no evidence for danger to the fetus or mother, to B, C, D and X, where the medical evidence indicates that the risk to the fetus outweighs any benefit to the mother. Laxatives should not be used during pregnancy without your physician’s advice. Certain products such as psyllium are called bulk laxatives. They are not truly laxatives, however. They are fiber which is healthy for the bowel and generally safe to take. Always consult your physician before taking any drug during or when planning pregnancy.


What are the effects on sexual function?

There are no known adverse effects of milk of magnesia on sexual function.


Are there other precautions?

Laxatives generally should be used only as a temporary measure. Prolonged, frequent or excessive use may result in bowel dependence or an imbalance in the blood minerals. Contact your physician if constipation persists or if there are any symptoms of bleeding, such as black or tarry stools or “coffee-ground” looking vomit. Milk of magnesia should not be used if nausea, vomiting or abdominal pain is present.


How long is it safe to take milk of magnesia?

This medication is for the short-term relief of constipation and should not be used for an extended period of time. Prolonged use can result in bowel dependence. In smaller antacid doses, the product can probably be used safely for long periods of time.


How about side effects?

Adverse reactions can occur with any drug, even over-the-counter medications. Some of these are mild such as a stomach upset, which may be avoided by taking the medication with food. Minor reactions may go away on their own but if they persist, contact the physician. For major reactions, the patient should contact the physician immediately.

For milk of magnesia, the following are the observed side effects:


  • nausea
  • vomiting
  • excessive diarrhea
  • weakness
  • faintness


A physician’s comment…

Milk of magnesia is an old standby for treating occasional constipation. This, indeed no laxative, should be used long-term without a physician’s evaluation of why the constipation is present. Even though unlikely, it is possible to take too much of this product and get too much magnesium into your body.