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Quinolones inhibit DNA gyrase and topoisomerase IV, blocking bacterial DNA replication and producing a bactericidal effect. Spectrum varies by generation, from early activity against urinary gram-negative bacteria to later agents with activity against organisms including Pseudomonas, S. pneumoniae, anaerobes, and MRSA. Absorption can be reduced by polyvalent cations, while clearance is mainly renal, with moxifloxacin as a hepatic-cleared exception. Uses span urinary, respiratory, gastrointestinal, skin and soft-tissue, and other infections. Their benefits must be balanced against serious warnings involving tendons, peripheral nerves, the central nervous system, and the aorta, as well as QT prolongation, interactions, and resistance. These points provide a foundation for selecting and evaluating the class safely.