• Combination of clinical success and microbiologic eradication (known as therapeutic response) at post-therapy visit.
  

• By patient and pathogen microbiologic and clinical responses at the post-therapy and post-study visits.
  

Levofloxacin has been approved in both its oral and intravenous forms to treat a large number of infections caused by bacteria. Levofloxacin and other members of a class of antibiotics known as fluoroquinolones have been used successfully to treat urinary and kidney infections. This study will compare the effectiveness and safety of levofloxacin given for 5 days to that of another fluoroquinolone, ciprofloxacin, given for 10 days in treating complicated urinary tract infection or acute pyelonephritis (kidney infection). A shorter course of antibiotics may help patients take all of their medication, which is critically important for curing the infection. A shorter course may also help prevent the development of bacteria that cannot be killed by antibiotics. Patients will take 750 milligrams of levofloxacin intravenously and/or by mouth once daily for 5 days or 400 milligrams of ciprofloxacin intravenously and/or 500 milligrams of ciprofloxacin by mouth twice daily for 10 days. To prevent the study doctor, study staff and patients from knowing which study drug they are taking, all study drug will manufactured to look the same and patients on the 5-day regimen will be given placebo for the last 5 days of their participation in the study. The intravenous infusion bags will be covered so that the solution cannot be seen. The objective of the study is to demonstrate that 5 days of levofloxacin once daily is at least as effective as 10 days of ciprofloxacin twice daily in treating complicated urinary tract infection or acute pyelonephritis.

Patients will take 750 milligrams of levofloxacin intravenously and/or by mouth once daily for 5 days or 400 milligrams of ciprofloxacin intravenously and/or 500 milligrams of ciprofloxacin by mouth twice daily for 10 days.