I assume giving antibiotics to rabbits is similar to giving one to humans. Once I got pretty sick and the doctor gave me a really high dose of antibiotics to kill the infections quickly. I mean those pills were freaking HUGE and I can tell you it was a very unhappy week for me as I had trouble using the restroom and I lost my appetite (I would throw up every time I ate). I had a real crappy time using the bathroom literally. I’ve read in numerous places if anybody or any animal is taking strong doses of antibiotics to fight an infection, then they should also be taking probiotics because the antibiotics kill both harmful and non-harmful bacteria in the digestive tract. I don’t think you can exactly overdose on antibiotics unless you give so much it literally kills all the good cells……
I know that at the store on this binkybunny website, they have stuff in the treats section (if i remember correctly) where they sell probiotic or digestive tract well being stuff. If you are getting increasingly worried, you could take a look at that and see if you would like to buy it. But it’s good that you are feeding your bunny critical care.