the culture (of your urine) likely revealed an organism that was not sensitive to the ciprofloxacin. this may be why there was a change in the antibiotic but you would need to talk to your doctor's office to confirm that this was the reason. another reason could be insurance coverage.
was prescribed 500mg ciprofloxacn then dr. prescribed 875 mg of amoxicillin after lab test for bladder infection. why?