This phase II trial studies ciprofloxacin compared to an inactive treatment (placebo) in diagnosing prostate cancer in patients undergoing removal of prostate cells or tissues for examination (biopsy). Ciprofloxacin is an antibiotic, a type of drug used to treat infections caused by bacteria. Giving ciprofloxacin to patients undergoing a prostate biopsy may help to lower abnormal prostate-specific antigen (PSA) levels caused by bacterial infection of the prostate gland and may or may not affect the detection rate of prostate cancer.