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Generic Name

polyethylene glycol (PEG)


Trade Name

Miralax (17 grams Powder )
Miralax is available as a Powder
This drug is also available as another trade name. Please click here to see the page on CoLyte, GoLYTELY.
This drug is not available in a generic form.


What is Miralax?

Miralax is a polyethylene glycol powder which dissolves in water. This material is not absorbed from the intestinal tract. It stays within the gut and acts to pull water into the intestine thereby increasing the volume and frequency of bowel movements.


What is it used for?

This preparation acts as a laxative for the treatment of constipation. It generally should be used for no longer than two weeks or as directed by the physician.


How do I take it?

The bottle top is a measuring cap marked to contain 17 grams of the powder (about 1 heaping tablespoon). Dissolve the powder in 8 ounces (1 cup) of water and drink. The physician may recommend a different dose or technique. It is best to take the mixture first thing in the morning. It can be taken on either an empty or full stomach.

Store this medication at room temperature. Keep all medications away from children. Never share your medications with anyone else.


How long or often should Miralax be taken?

It may be necessary to use this medication for 2 to 4 days before a bowel movement occurs. It is recommended that Miralax be taken for no longer than 2 weeks.


Are there interactions with food or beverages?

There are no known food or beverage interactions with Miralax. An increase in fluid intake, a diet rich in fiber or bran, and regular exercise can improve bowel regularity.


Are there interactions with other drugs?

An interaction generally means that one drug may increase or decrease the effect of another drug. There are no known interactions with Miralax. However, since a laxative effect may occur, other medications should not be taken at the same time because they may be swept down the intestine before they are dissolved and absorbed.


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 another disease. Generally, no laxative should be taken with certain intestinal or other diseases that can cause diarrhea. Discuss this with the physician.


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 Miralax if there has been a previous reaction to this or a similar product.


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. Miralax is ranked C, meaning safety has not yet been demonstrated in pregnancy. Always consult your physician before taking any drug or product during or when planning pregnancy.


What are the effects on sexual function?

There are no known adverse effects of Miralax on sexual function.


Are there other precautions?

  • Always take Miralax with at least 8 ounces of water. This will allow the medication to work and helps to alleviate constipation.
  • What about diet? Fiber increases stool bulk and is a very important part of any constipation program. Therefore, a high fiber diet is almost always recommended. (See Link below.)
  • Safety in children has not been established.

Contact your physician if constipation persists for more than a week after starting Miralax or if rectal bleeding occurs.


How long is it safe to take Miralax?

Miralax can be used periodically long-term. It should only be used for 14 days with a 2-4 week period of abstinence between use.


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 Miralax, the following are the known side effects:


  • cramps
  • nausea
  • bloating
  • diarrhea


  • excessive diarrhea
  • severe weakness
  • severe dehydration


A physician’s comment…

Miralax is the first FDA approved new laxative in over 20 years. This product was initially used to cleanse the colon prior to a colonoscopy exam. It was then modified for use as a laxative. It basically works by a flushing action. It causes a great deal of water to be retained in the bowel which acts to flush everything along in it’s path. The ideal “laxative” would be one that causes the large bowel to contract more often and so move soft formed stool to the rectum regularly. This action would return the colon to its normal function. There are some drugs now in the experimental stages which seem to have this effect.

Increased fiber intake is recommended for constipation.