Pharmacokinetic and pharmacodynamic properties of antimicrobials in the therapy of respiratory tract infections.

Antimicrobial pharmacodynamics examines the relationship between the pharmacokinetics of a drug over time and its treatment effect. Pharmacokinetic/pharmacodynamic parameters have been shown to be predictors of the antimicrobial activity of a variety of drugs. The pharmacodynamic parameter linked to efficacy has been demonstrated to vary for different antimicrobial classes. Within an antimicrobial class, the magnitude of the pharmacodynamic parameter predictive of efficacy has been shown to be similar, as long as free-drug levels in serum are considered. Treatment outcome predictions based upon parameter magnitudes have correlated well and have been useful for assessing the future course of both susceptible and resistant pathogens of the respiratory tract. This has been useful for the development of susceptibility breakpoints and antimicrobial treatment guidelines. Recent studies have begun to investigate the relationship between antimicrobial pharmacodynamics and the prevention of drug resistance.