We at one point stopped miralax because it gave her bad gas. It was bad enough to not be able to poop but then to have gas on top of it made it worse.
Finally was educated by a great peds Dr. (Dr Shah) that even if it were so bad they'd have to admit her, they would only give high doses of oral miralax.
We went home and I became aggressive. My baby was hurting so bad she was now sitting in the bathroom most of the day screaming and crying. So, a dose of laxative 1200 x the amount suggested, along with miralax, spa, castrol oil and daily enemas and we got relief in 4 days.
We now have to rehab the intestine with daily miralax for the next 6 months.