Is Miralax Safe?

Constipation is one of the most common problems that affects kids. Sometimes it's mild and changes to diet and routines can help sufficiently. But if it's more severe or if kids are resistant to change, Miralax is my go-to treatment. Some parents question the safety of it though. What are their concerns?

Constipation is one of the most common problems that affects kids. Sometimes it’s mild and changes to diet and routines can help sufficiently. Those are of course the ideal treatments. But if it’s more severe or if kids are resistant to change, Miralax is my go-to treatment. Several parents have asked me about its safety due to what they’ve seen online. I know many more are probably worried but just haven’t asked. With all the concern, I thought I’d share some of the concerns and reasons that I still recommend it.

What is Miralax?

Miralax has been used since 2000, and since I finished my pediatric residency prior to that, I can remember the alternatives we used previously. Many of them were difficult to get kids to take due to poor taste or grittiness. When Miralax was first available, treatment of constipation improved significantly due to the tolerance and acceptance by kids. It was initially available by prescription only and expensive – thankfully both of those hurdles have been removed.

Miralax is the brand name for polyethylene glycol 3350 or PEG 3350. It is now available as an over the counter medication, so no prescription is needed. Generic versions are available. It has been used by many kids over many years, often for long periods of time, to treat constipation.

Is it a laxative?

PEG3350 is a stool softener, not a laxative (despite the name).The molecule binds to water, but is too large to be absorbed through the gut so it passes through the gut and carries the water with it. It works by increasing the water content of the stool. The more PEG taken, the softer the stool.

PEG is not a laxative and should not cause cramps. It is not habit forming. As mentioned above, it is not absorbed into the body it just goes through the GI tract and leaves with the stool.

How is it used?

PEG 3350 is a tasteless powder that dissolves in liquids. It often needs to sit for a few minutes and re-stirred to fully dissolve.

It may be dissolved in water, with a slight change to its taste, but is palatable. Be careful of adding it to drinks high in sugar (even juice), since your child may be on it for a long time, and they don’t need the added sugar. Consider making flavored water with your child’s favorite fruit. Simply put cut up fruit in water in the refrigerator for a couple hours. Infused water tastes great and is a healthy base for your Miralax mixture – or anytime your kids need a drink and don’t like plain water.

I don’t recommend adding it to carbonated beverages.

I recommend mixing a capful of powder in 8 ounces of water and titrating the amount given based on need. My office website discusses this in detail.

Why do we need medicine?

Constipation is common.

Very common. It causes pain, poor eating habits, fear of toileting, and sometimes even leads to ER trips and CT scans. It can last months to years in some kids, so it is not a minor issue when kids suffer from it.

Diet changes are hard – especially in kids!

Kids are often constipated because they have a diet that is poor in water and fiber. They need to eat more fruits, vegetable and whole grains. Many kids drink too much milk and eat too much cheese.

Changing habits is very difficult in strong willed kids. When it comes to food, they’re all strong willed! Dietary changes of course should be done so they are healthier on many levels, but if their stomach hurts all the time, they are unlikely to get out of their comfort zone with foods. Habits change too slowly to help the constipation if used alone.

I encourage first changing the diet to help constipation, but if that fails, or if it is too significant of a problem, PEG 3350 is my first choice. I have recommended it for years without any known side effects or complications, other than the kids who have frequent watery stools on it. This usually responds to continuing the medicine to release the large stool mass that has built up. Some kids just need to decrease the dose a bit.

What’s the concern?

I was quite surprised in 2015 to see that researchers were starting a study on the drug. It surprised me not only because I’ve never heard valid concerns about the safety or efficacy of the medicine (I have seen some really weird stuff online, but nothing that is valid), but also because I’ve never seen headlines that a study is starting. Usually headlines report results of studies. Why did it hit the press before the study was even done? I have no idea.

Even more interesting… it seems the study hasn’t started yet. Three years later. Not a high priority, apparently. Which fits with the low level of concern I find among general pediatricians and pediatric gastrointestinal specialists.

Yet parents still ask about the risks.

What was the proposed study?

Initial reports stated that they were going to look at the safety of other molecules in the PEG 3350.

PEG 3350 itself is a very large molecule that isn’t absorbed by the gut, but there are concerns that smaller compounds could be found as impurities in the manufacturing process of PEG 3350 or formed when PEG 3350 is broken down within the body.

The question is if these smaller compounds are absorbed by the gut and accumulated in the bodies of children taking PEG 3350.

Some families have reported concerns to the FDA that some neurologic or behavioral symptoms in children may be related to taking PEG 3350. It is unclear whether these side-effects are due to PEG 3350 since neurologic and behavioral symptoms can lead to constipation.

What are the recommendations?

The 2014 guidelines for constipation diagnosis and management from the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition support the use of PEG 3350: Evaluation and Treatment of Functional Constipation in Infants and Children: Evidence-Based Recommendations From ESPGHAN and NASPGHAN.

These guidelines basically state that not many studies are required to diagnose functional constipation after a thorough history and exam. This means that we don’t need to do expensive tests to make the diagnosis.

The common things we recommend (fiber, water, probiotics) don’t have any proof that they work. There is evidence that PEG 3350 works.

Why does the label say it’s for adults?

As a pediatrician I know that many (if not most) of the medicines we use in children are not tested in children before they come to market.

Historically once something is approved in adults, physicians start to use them in children. Companies generally don’t invest money in studies to expand uses after approval because they know that the products will be used in broader ways without the specific indication. They don’t want to spend money they don’t need to spend, which makes sense from a business perspective. It’s also more difficult to do studies in minors.

New rules encourage pediatric testing, but all the drugs previously used in children will not need to undergo this testing. Because they’ve been used for years, we rely on post-market safety data.

Are there studies in children?

Many of the news articles say that studies have not been done in children, but this isn’t true.

This 2014 research article reviews the history of PEG 3350 and compares to other medicines used in pediatric constipation. It also shows safe blood electrolyte levels while on PEG 3350 long term.

In 2001 a study was published showing safe and effective pediatric dosing.

2003 studyshowed safety and better tolerance than previously used medications for constipation.

A study specifically looking in children under 18 months of age showed safety.

2009 Canadian study shows its safety in children.

If you look at the references of any of these studies, you will find more. The only side effects noted are related to diarrhea, cramping, bloating — all things that would be expected with a large stool mass blocking the new, softer, water filled stools from coming out. Once the large stool mass is out, these symptoms resolve.

For what is PEG approved?

PEG is used in many products, not just stool softeners. It is found in ointments and pills to allow them to be more easily dissolved in water. PEG can also be found in common household products such as certain brands of skin creams and tooth paste.

PEG 3350 is approved for treatment of constipation in adults for up to 7 days. Approval is based on studies available at the time a medicine is approved. Many commonly used medications are not specifically FDA approved for use in children less than 16 years due to difficulties and expense in testing drugs on minors.

How do we know it works?

There have been several studies in children and the collective experience of pediatricians around the world showing improved tolerability over other treatments for constipation because PEG 3350 has no taste, odor, or texture.

It has been shown to be either as effective or more effective than other constipation treatments. See the links to these studies above. Until children can keep stools soft with adequate amounts of water, fruits, vegetables, and fiber, long term use of PEG is well tolerated.

How long can PEG be used in children?

This is a very difficult thing to study because the longer a study follows their subjects, the more subjects are lost to follow up.

There have been studies of up to 30 months that showed safe use. Blood electrolytes, liver and kidney tests were all reassuring that PEG is safe during the study.

Pediatric gastroenterologists and general pediatricians have often recommended even longer periods of time without any known side effects.

If my child has taken PEG 3350, should I worry?

Is miralax safe?
Is MiraLAX safe?

I cannot stress enough that the studies that have been done all support the safety and efficacy of PEG 3350.

After years of experience using PEG 3350 with many children, I have not seen any neurologic or behavioral problems caused by PEG 3350. I do see many kids with baseline neurologic and behavioral problems become constipated, so they often end up on PEG 3350, but if the issue is carefully assessed, the problems start prior to the treatment.

Generally if the stools are softer, you can more easily work with the behavioral issues that cause the constipation, such as loss of appetite/poor diet and failure to sit on the toilet long enough to empty the stool from the rectum.

If you decide it is time to stop the medicine, be sure to discuss this with your child’s doctor to keep them in the loop about how things are going!

Author: DrStuppy

I am a pediatrician and mother of two teens. I have a passion for sharing health related information.

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