Miralax for Constipation in Children

Resting among the myriad of OTC medications available to treat constipation in infants and children is the little known powder dubbed polyethylene glycol (Miralax).  Prior to October 2006, polyethylene glycol was available by prescription only, but after much review, it landed on the FDA’s Rx-to-OTC Switch List and started appearing on drugstore shelves throughout the country.

Although polyethylene glycol is only FDA approved for patients 17 and up, clinicians are prescribing the medication more often to treat constipation in infants and children.  As clinical experience with polyethylene glycol increases in our pediatric population, so does awareness of its OTC existence.  For this reason, it seems appropriate to provide a brief discussion about this medication.

Why the Doctor might prescribe polyethylene glycol…

Clinicians would prescribe polyethylene glycol to your child to treat impaction and constipation that is not related to a serious illness (i.e. gastrointestinal disease, diabetes, cystic fibrosis, etc.).  Constipation can be defined as a delay in defecation or difficulty in having a bowel movement for more than two weeks.  Polyethylene glycol can be used for both acute and chronic constipation.

Impaction would be described as a condition where dry, hard stools form into a mass that collects in the rectum.  The mass makes it very difficult, if not impossible, to have a bowel movement.

Once the impacted stool has been evacuated or if impaction was not present to begin with, maintenance therapy would be implemented to help your child sustain normal bowel movements.  Polyethylene glycol used for maintenance therapy will improve stool frequency and/or consistency and ease your child’s pain and discomfort.

The dose needed to bring about disimpaction will be higher than that used in maintenance therapy; but nonetheless, polyethylene glycol has been proven to be an effective option in both scenarios.

Mechanism of Action

Polyethylene glycol falls into the class of medications known as osmotic laxatives.  The way the medication works is very straightforward: it decreases the amount of water absorbed from your intestines, which thereby increases the amount of water in your stools.  This increase of water content in your stools makes the stool softer and easier to pass.

It may take less than a day for polyethylene glycol to do its job, but do not be surprised if it takes 2 to 3 days for your child to have a bowel movement.  If faster relief is needed, it may be a good idea to explore other medication options!

Precautions and Side Effects

Adverse reactions to polyethylene glycol may include cramping, abdominal bloating, gas, diarrhea, and nausea.  Serious adverse reactions to polyethylene glycol are not common at all.  There is a very rare chance that your child could be allergic to polyethylene glycol, in which case your child may present with hives, rash, dizziness, difficulty breathing, or swelling of the face, tongue, or throat.  The medication should be discontinued and a physician should be consulted if an allergic reaction does occur.

There is limited information from quality studies on the use of polyethylene glycol in children less than 2 years of age.  That’s not to say this medication should not be used in infants.  In fact, prescribers have been progressively increasing their orders of polyethylene glycol for babies less than 6 months old even without the evidence from strong studies.  Just be sure to keep an extra watchful eye on your infant while their taking polyethylene glycol!

In the case of chronic constipation, you should wean your child off polyethylene glycol once the goal of therapy, about one soft stool per day, is achieved (it may take months to get to this point).  Taper the dose down every 2 weeks until daily movements continue without the laxative.  If you discontinue the polyethylene glycol in a cold turkey kind of way, hard stools will likely recur!

Other Common Osmotic Laxatives

Lactulose, sorbitol, Milk of Magnesia, and magnesium citrate are all osmotic laxatives that work in a similar fashion as polyethylene glycol.  Studies show they all have comparable efficacy, but recent findings suggest that polyethylene glycol has fewer side effects and greater acceptance by children.

The increasing comfort in using polyethylene glycol in infants and children is good news because magnesium citrate and Milk of Magnesia are a bit frightening due to possible magnesium poisoning in the littlest patients.  In addition, since Lactulose and sorbitol have a terrible taste, polyethylene glycol just offers a way out of the ensuing battle of getting your child to take a medication needed to relieve their constipation.  Polyethylene glycol is a well-accepted medication by an otherwise finicky group of patients!


Although polyethylene glycol is available over-the-counter and gaining ground in its use in infants and children, I would recommend bringing your child to their physician before starting this medication as the underlying constipation needs a workup first.

If the physician decides the issue needs to be treated, it may be in your child’s best interest to start with behavior modification and dietary changes before bringing polyethylene glycol on board.

Once it’s determined that a medication is needed to help relieve your child’s constipation, typical age-based dosing used in clinical practice is as follows: younger than 18 months – ½ to 1 teaspoon once daily; 18 months to 3 years – 2 to 3 teaspoons once daily; older than 3 years – 2 to 4 teaspoons once daily.

The teaspoon measurements refer to the amount of polyethylene glycol powder you would mix with 4 to 8 ounces of water, juice, or other flavored beverage (hot, cold, or room temperature).  The mixture can be taken without regard to meals and at any point during the day.

There are specific weight-based dosing guidelines available, but regardless, I would verify the dose with your child’s physician or pharmacist just to be sure you are giving your child a safe, yet effective, amount.

If your child’s physician suggests buying the OTC polyethylene glycol, it may be beneficial to ask them for a prescription instead because most insurance companies still cover the prescription version.  The prescription formulation is the same as the OTC product, comes in generic, and is equally effective and safe.  It’s definitely worth the trip to the pharmacy because as we all know, a penny saved is a penny earned!

Whoa, I know that was an eyeful, but please let me know if you have any questions or need more information by leaving a comment below or e-mailing me at Cate@getpharmacyadvice.com.

I know you’ve already heard, but we have this fabulous video course available for free that will teach you how to save money on your prescription medications.  It’s all your’s so long as you click here!

Peace out for now!


  1. Hi Cate,
    We have battled constipation with my now 2 year old for the past year but the initial bm problems started when she was much younger. Anyway, after making adequate changes to her diet, she still had problems that about 3 weeks ago landed us in the hospital, where the doctors said her colon was enlarged from the chronic constipation and that she needs to be on a daily dose of miralax for 6-12 months.
    Here’s my question:
    I’ve realized, after much research, that although Olive’s diet was great, it didn’t contain very much fiber. We’ve been on a 17g daily dose now for 3 weeks and just recently has she started having multiple (2-3) very runny bms. The doctor told me to cut back on the daily dosage but I can give her the 17g dose everyday and each day is different. Some days completely soft normal bms, and the next too runny.
    Thanks for you help and advice!

  2. My 10 yr old nephew is badly impacted according to xrays. His pediatrician prescribed 1cup of miralax a day – this seems to me to be an unsafe amount. What are your thoughts? He was given it yesterday and today and cant stay out of the bathroom and has had several accidents and is missing school. Im going to guess he ways around 70 lbs.

  3. Hi Tessie, Thank you for coming by the site! I would definitely check again with the physician. It is quite possibly by “1 cup” she meant “1 capful”. Please check with his physician because 1 cup would definitely be an overdose.


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