When you stop using a proton pump inhibitor (PPI) a spike in stomach acid production is inevitable. That’s right, inevitable. So your child will very likely be in pain. This does not necessarily mean that the wean has failed. You need to consider pain management for the duration of the wean which could be several weeks. Talk to your doctor about appropriate pain management during this time.
Here’s why: the body will produce a hormone to tell the body to start producing acid again. The acid needs to reach a certain level before the body will realise it can stop and levels will normalise. In the meantime, you need to expect that stomach acid production will be a bit haywire.