Using pharmacodynamic and pharmacokinetic surrogate markers in clinical practice: optimizing antimicrobial therapy in respiratory-tract infections.

Pharmacodynamic and pharmacokinetic surrogate markers and their relationship to outcomes in respiratory-tract infections are reviewed. While several limitations affect the universal application of antimicrobial pharmacodynamic principles in clinical practice, recent studies have suggested that these principles may allow optimization of selected therapies. For the fluoroquinolones, the pharmacodynamic variable that has been correlated with antimicrobial efficacy is the ratio of the area under the serum concentration-time curve to the minimum inhibitory concentration. On the basis of their pharmacodynamic profiles, the newer fluoroquinolones, including such investigational agents as gatifloxacin, should produce satisfactory clinical and microbiological outcomes against pathogens commonly associated with community-acquired respiratory-tract infections. An assessment of the individual agent's pharmacodynamic profile will assist in choosing the best fluoroquinolone regimen; however, consideration should also be given to the agent's adverse-event potential.