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

Pharmacodynamic and pharmacokinetic surrogate markers and their relationshi p 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 sugge sted that these principles may allow optimization of selected therapies. Fo r the fluoroquinolones, the pharmacodynamic variable that has been correlat ed with antimicrobial efficacy is the ratio of the area under the serum con centration-time curve to the minimum inhibitory concentration. On the basis of their pharmacodynamic profiles, the newer fluoroquinolones, including s uch investigational agents as gatifloxacin, should produce satisfactory cli nical and microbiological outcomes against pathogens commonly associated wi th community-acquired respiratory-tract infections. An assessment of the individual agent's pharmacodynamic profile will assist in choosing the best fluoroquinolone regimen; however, consideration shoul d also be given to the agent's adverse-event potential.