Ciprofloxacin hydrochloride, C17H18FN3O3 •HCl•H2O, is a synthetic broad-spectrum antibacterial agent. Ciprofloxacin differs from other quinolones in that it has a fluorine atom at the 6-position, a piperazine moiety at the 7-position, and a cyclopropyl ring at the 1-position. it was the drug of choice forcombating anthrax. Ciprofloxacin hydrochloride (Cipro, 500-mg tablets) is highly active against the important bacterial causes of enteritis, including diarrheogenic Escherichia coli, Vibrio cholerae, Salmonella species, Shigella species, Campylobacter jejuni, Aeromonas species, and Yersinia enterocolitica.