Pharmacodynamics of antiinfective therapy: taking what we know to the patient's bedside

Applied pharmacokinetics has long been a lifeline of clinical pharmacy services. National surveys during the past decade documented clinical pharmacy services and demonstrated that a substantial rate of growth occurred in clinical pharmacokinetic consultations and management of drug therapy protocols. Pharmacodynamic principles of antiinfective agents are rapidly becoming a new paradigm of clinical pharmacy services. beta-Lactams, aminoglycosides, and fluoroquinolones represent the three classes of antiinfective agents that have made the most progress toward the clinical applications of pharmacodynamics. Pharmacodynamic parameters are being used to select and compare agents within an antiinfective class (e.g., fluoroquinolones), make modifications in the dosage (e.g., extended-interval dosing of aminoglycosides) and/or mode of administration (e.g., continuous infusion of beta-lactams), develop in vivo breakpoint determinations, and assess the development of bacterial resistance. In addition, pharmacodynamic parameters have influenced the clinical drug development of new (e.g., linezolid) and older (amoxicillin-clavulanate, fluoroquinolones) antiinfective agents. Further investigations are needed to explore the clinician's use of validated prediction methods and patient-specific pharmacodynamic parameters at the bedside. By linking pharmacokinetic services with pharmacodynamic principles, the opportunity for continued progress toward our assessment and decisions for successful clinical outcomes is possible with old and new antiinfective agents.