Dear patient, yes, since apparently the sulfatrim didn t get a hold of the infection, the switch to a more broadband substance like Noroxin is the right thing to do. I am sure your bladder infection and urethritis (both goes hand in hand usually) will get better soon with this. If not, there should be a 3 day antibiotic pause (if symtoms allow), and then the urine should be tested with an antibiogramm/ bacterial culture to find out which antibiotic works best. Also then an ultrasound of the bladder and kidney is advisable to rule out any other conditions. Hope this is helping you , if you have any clarificatons you can get back to me, if this was helpful please kindly rate my answer. Best regards