PHARMACODYNAMICS OF ANTIMICROBIAL THERAPY IN SURGERY

INTRODUCTION: ''Pharmacodynamics'' refers to the relationship of drug concentrations in serum or tissues to effects on biologic systems, Con cepts used to describe antimicrobial pharmacodynamics include the mini mal inhibitory concentration (MIG), the minimal bactericidal concentra tion (MBC), and serum bactericidal titers (SET), as well as post-antib iotic effect. METHODS: Pertinent published literature was identified t hrough a MEDLINE search. RESULTS: Aminoglycosides have a concentration -dependent effect on bacteria killing and possess a relatively long po stantibiotic effect. Given these characteristics, single-daily dosing, where the total daily dose with a traditional aminoglycoside regimen is given as one dose, may be more efficacious compared with more frequ ent dosing. For beta-lactam antimicrobials, bacterial killing is relat ed to the duration of time that the free drug concentration exceeds th e bacterial MIG. Beta-lactam antimicrobials have been shown to have no , or a short postantibiotic effect, Beta-lactam antimicrobials may be more effective when administered as continuous intravenous infusions. CONCLUSIONS: Pharmacodynamic variation may result from differences in drug sensitivity among individuals and the nature of the interaction b etween antimicrobials and microorganisms. Proper use of pharmacokineti c and pharmacodynamic principles can result in more effective and less toxic antimicrobial regimens.