Do I have to use rifaximin if my child is older?

No. Inulin can be started in a child of any age but just be aware that the older the child, the less likely the inulin will work at the beginning. And if inulin does seem to be helpful, its positive effects may not last very long.nnThat being said, I have cared for many older teenagers who have a positive response from inulin that lasts several years.