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Pediatrics/Issues with Miralax and diarrhea in a preschooler


My four year old was recently diagnosed with constipation and encopresis, so the Pedi prescribed a regimen of Miralax.  We did a cleanout of 17mg in 8oz of liquid and I was to give 4 oz in the morning and 4 oz in the evening for 4 days Then, the maintenance dose was 17mg in 5-7oz once daily with "tritration".  

During the clean out, it was awful, with stool that was practically liquid.  Then once we got to the maintenance dose, he continued to have extremely runny stool, so after doing a little looking around online, I saw that many parents were only giving their children half a cap full or 1 tsp of miralax a day,  So I cut back the dosage to half a cap full and now I am trying 1 tsp a day.  However, he is still having very runny, applesauce-like consistency BMs and only going every other day.  Should I drop the dose to 1/2 tsp a day or just give a dose every other day?

I tried calling our Pedi, but they haven't been much help, except to tell me that it should eventually stabilize...However, it's been almost a month and we're still having diarrhea.  It's affecting him a preschool, and they could possibly not let us return next Fall if we don't get this under control as they expect the children to be potty trained and he's having terrible, runny accidents every other day. Any advice would be great appreciated.

Hi, Rachel,

Generally the issue with continued runny stools is an insufficient initial cleanout, causing the newly formed liquid stool to leak out past a stool mass that is still present.  I generally suggest a new cleanout w one cap twice a day for 2-3 days and then start back with a cap a day.  If the cleanout is successful, the stools should be soft and manageable.  I also like to have parents engage the gastrocolic reflex, the reflex that causes us to feel like we have to go after meals.  This means trying to go, in a non-punitive way, after each meal.  

Your child may have different mechanisms for all this and of course run anything by your pediatrician.
This advise assumes that the bowels are only temporarily out of whack and that there are no congenital structural/functional problems.

Good luck, dr. Olson


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David Olson, MD


I would be happy to attempt to answer any questions about general pediatric topics, either medical issues or behavioral issues. This would include all the various questions one receives in a busy pediatric practice. I`m a board certified pediatrician in northern Michigan and have been in practice for over 15 years. I enjoy the teaching role I have in our practice and would enjoy the opportunity to help others with their pediatric problems.

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