Pharmacokinetics and pharmacodynamics of fluoroquinolones in the respiratory tract.

Pharmacokinetic and pharmacodynamic features are important predictors of the therapeutic efficacy of an antibiotic. In respiratory tract infection, study of the clinical implication of pharmacodynamic features is complicated as infection occurs at several distinct sites. To ensure microbiological efficacy, antibiotics should not only be active against common respiratory pathogens but should also penetrate to the sites of infection. The newer fluoroquinolones combine good activity against Gram-negative and "atypical" organisms with extended Gram-positive activity, and are unaffected by penicillin susceptibility status and beta-lactamase production. Long terminal half-lives allow once-or twice-daily dosing, and a concentration in lung tissue at levels many times higher than is observed in the serum. Although the benefit of antibiotics in some lower respiratory tract infections has been questioned, they have proved effective in community-acquired pneumonia and acute exacerbations of chronic obstructive pulmonary disease. Early studies of oral fluoroquinolones versus intravenous or oral treatment with one or more agents in community-acquired pneumonia have shown promise. Although resistance is a potential problem with increased fluoroquinolone use, its rapid development is not anticipated. In conclusion, the broad-spectrum antimicrobial activity, tissue distribution and safety profile of fluoroquinolones suggest that they have a place in respiratory tract infection.