My son was on cough syrup with codeine. I think his was phenegran with codeine. He had a cough from sinus issues and his GP pxed it. His GI okayed it.
The only problem he had was that that the codeine can cause things to back up so he became constipated. Once we figured out the codeine component and added miralax all was well. During this time he was on Remicade as well and there was no interaction issues. A call to your GI nurse or the on call GI can further allay your concerns.