About 4 months after my last klonopin, I got a uti and the Dr prescribed bactrim and I got anxious on it. Not horrible, but I did get anxious after 3 days, so I called the Dr and changed it to amoxicillin and had no problems with that. Bactrim works through the central nervouse system I found out. I also would take the most recent drug not some old drug that may not be good any longer and you dont have a full prescription for I would guess. Also, you should always finish your complete prescription of an antibotic, just as an FYI.
Good luck! I dont think you should have nay problems, but I do understand your aprehension.