Ciprofloxacin is a fluoroquinolone (flor-o-KWIN-o-lone) antibiotic, it is used to treat different types of bacterial infections. It is also used to treat people who have been exposed to anthrax or certain types of plague. Ciprofloxacin extended-release is only approved for use in adults. Fluoroquinolone antibiotics can cause serious or disabling side effects that may not be reversible.