Before he took it, we hadn't heard anything bad about it, either. In fact, I was under the impression that it's actually quite a good treatment for SIBO.
We later learned that Rifaximin kills off both bad and good E. coli, and his good E. coli was likely really low to begin with. After he did a good course of Mutaflor (E. Coli Nissile 1917) he got MUCH better. It took us awhile to even get a grip on what the problem was and we didn't realize the Rifaximin was actually contributing to the problem.
I'm glad to hear you're doing better.
How did you discover that rifaxamin killing the low E. coli was the problem? One of the most frustrating aspects is poor diagnostics... so many ch is trial and error