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Medications > All About Miralax

All About Miralax

What is Miralax?

Miralax is a stool softener. The active ingredient, polyethylene glycol (PEG), 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. It is not absorbed into the body. It can be used as long as it is needed without concern. It is tasteless and dissolves easily in liquids such as juice, Kool Aid, and Crystal Light. It may be dissolved in water, with a slight change to its taste, but is palatable.

How do I mix and measure PEG?

PEG comes as a white powder in a bottle with a measuring cup. The measuring cap has a line on the inside labeled “17 grams”. Simply fill the cap to that line and mix with 1 cup (8 oz.) of water, juice, Crystal Light, or other non-fizzy liquid. Any non-carbonated (not fizzy) drink is OK, but sugar free drinks may be less likely to cause gas and cramps. Since this will be taken for a long period of time the extra sugar calories in juice and other sugary drinks will add many empty calories to the diet. It takes about 5 minutes of occasional stirring to dissolve. It is important to always mix PEG in this proportion: One capful (17g) to 8 oz. liquid. If you wish, you can mix more than 8 oz. at a time. For example, if you make 8 cups (2 quarts) of liquid with 8 capfuls of PEG. Keep this in the refrigerator and pour the dose from this supply.

How much should I give?

The chart below will help guide your dosing. You may give the “Overnight relief” dose the first day if your child is impacted (as directed by your doctor) and then start the chronic constipation daily dose the following day. Your child should have 2-3 milkshake consistency stools per day. If the stools are too hard or not frequent enough, increase the dose. If the stools are watery or too numerous, decrease the dose. “Diarrhea” is common at the beginning of treatment because of stool leakage around an impacted stool. Simply decrease the dose. You may change the dose in small increments every 3 days. The dose is changed by how many ounces of the liquid are given, not by how it is mixed. The average time to treat constipation is 8 months, with a range of 6-12 months, so don’t stop too prematurely, especially if potty training or family changes are occurring. Use the Bristol Stool scale below to keep track of what the stools look like. Ideal stools are 3-4 in children (not infants). If the stools are 1 or 2, increase the Miralax. If they are 3, 4, or 5, keep it the same or lower the amount slightly. If they are 6-7, consider leakage around a large stool mass or diarrhea. Altering the miralax dose will depend on the cause.
 

Body Weight (lbs)

Chronic Constipation

Overnight Relief (may take longer than 1 day)

20 3 oz. daily 4 oz. twice daily
30 4 oz. daily 4 oz. twice daily
40 5 oz. daily 5 oz. twice daily
50 6 oz. daily 6 oz. three times daily
60 8 oz. daily 6 oz. three times daily
70+ 8 oz. daily 6 oz. three times daily
 

How long do we use Miralax?

Miralax should be used until a child can easily pass stools daily that are a 3-4 on the scale below. Most children need to be on the Miralax for 6-12 months. This seemingly long time allows the child to not only get in the habit of stooling on a regular basis, but also allows time for dietary changes to help keep stools soft without the aid of Miralax. See our Constipation page for good foods to eat to help with keeping the stools soft.

When a child is constipated, the gut stretches to hold extra stool. This gut muscle must get back into shape in order to stool properly. This can take quite a bit of time, just like getting any other muscle into shape. If the Miralax is stopped prematurely, the stools quickly back up again.

Most kids need 6-12 months of regular Miralax use. This regular use generally starts 1-2 times/day, but can wean down to a few times per week if they eat enough high fiber foods and drink enough water.

Miralax Safety

 Please visit Dr. Stuppy's blog on Miralax safety. 
 

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