The Role of Pharmacodynamics in Effective Treatment of Community-acquired Pathogens*

Pharmacodynamics is commanding a greater role in the study of antibiotic efficacy and determination of dosing regimens. The simple measurement of serum, tissue, and body fluid antibiotic concentration do not provide sufficient information concerning the rate of pathogen killing at the site of any postantibiotic effects that may be occurring. This article discusses the pharmacokinetic and pharmacodynamic parameters that are now being used to determine antibiotic dosing regimens and will be used to set new breakpoints of susceptibility. Understanding the relationship between the 24-hour area under the serum concentration vs time curve, the minimum inhibitory concentration, and the peak serum level can have profound effects on the appropriate antibiotic choice for a given infection and the dosing regimen. This article will provide an overview of the key pharmacodynamics studies in animals and humans with a focus on pathogens associated with community-acquired infections. (Advanced Studies in Medicine 2002;2(4):126-134) H istorically, an antibiotic dosing regimen has been determined by pharmacokinetic (PK) parameters. However, pharmacodynamics (PD) play an equal, if not more important, role because the drug concentrations in the tissues and body fluids as well as at the site of infection are considered. Tissue and body fluid concentrations determine the pharmacological and toxicological effects, while drug concentration at the site of infection determines the antimicrobial effect. In this age of increasing antibiotic resistance, pharmacodynamics becomes even more important because these parameters may be used to counteract and/or prevent resistance.