Miralax (PEG 3350) for childhood constipation: Is it safe?

by William W. Long, MD, FAAP

There have been recent reports about children on Miralax® osmotic laxative and psychiatric side effects.  Reports of this type and questions of Miralax safety first came out in 2012, and have resurfaced on social media in the past several months.

The Children’s Hospital of Philadelphia is conducting a safety study of Miralax in children, partly in response to some of these reports in 2012.  This is not because there is widespread worry.  This is because as science-based physicians, we want to make sure our evidence is continues to be tested and proven when we are treating our patients.

What is Miralax?  It is a large molecule that is commonly called a polymer in chemistry terms.  The generic name for the laxative is Polyethlene Glycol (or PEG).  It is a connected chain of many ethylene glycol molecules.  This sounds kind of scary because ethylene glycol is what is in antifreeze.  But PEG is something different.  It works by staying in your intestinal tract (which technically is outside your body) and helping to keep water in the intestines to make the stools softer.  It does not break down in your body into antifreeze or anything else.

Multiple studies in thousands of children have shown PEG to be a safe treatment for constipation.   This laxative has a very low side effect profile compared to other laxatives used in children.

That being said, there can be incidents of intolerance to these agents, just like someone can have an intolerance of certain foods, or gluten.  It is rare, but can happen.

But, if a rare reaction to PEG occurs, it will not cause any permanent harm if it is stopped.

Constipation is a common, sometimes serious problem in children that can lead to lifelong bowel issues and sometimes severe illness and hospitalization.  The first line of treatment for constipation is a well-balanced diet, with plenty of water, and exercise (yes, running around can make your bowels move better!).  For patients who have more severe problems, Miralax (PEG) is a very safe laxative that can be given to almost all patients for years at a time.

Please see our recent Dr. Notes article by Dr. Burns on constipation for more information on this condition.