Ciprofloxacin. Molecular model of the antibiotic drug ciprofloxacin (C17.H18.F.N3.O3). This is a second-generation fluorineoquinone antibiotic used for treating a large range of infections. It is one of the most commonly prescribed antibiotics. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red) and fluorine (cyan).