Applied pharmacokinetics has long been a lifeline of clinical pharmacy serv
ices. National surveys during the past decade documented clinical pharmacy
services and demonstrated that a substantial rate of growth occurred in cli
nical pharmacokinetic consultations and management of drug therapy protocol
s. Pharmacodynamic principles of antiinfective agents are rapidly becoming
a new paradigm of clinical pharmacy services. beta -Lactams, aminoglycoside
s, and fluoroquinolones represent the three classes of antiinfective agents
that have made the most progress toward the clinical applications of pharm
acodynamics. Pharmacodynamic parameters are being used to select and compar
e agents within an antiinfective class (e.g., fluoroquinolones), make modif
ications 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 b
acterial resistance. In addition, pharmacodynamic parameters have influence
d the clinical drug development of new (e.g., linezolid) and older (amoxici
llin-clavulanate, fluoroquinolones) antiinfective agents. Further investiga
tions are needed to explore the clinician's use of validated prediction met
hods and patient-specific pharmacodynamic parameters at the bedside. By lin
king pharmacokinetic services with pharmacodynamic principles, the opportun
ity for continued progress toward our assessment and decisions for successf
ul clinical outcomes is possible with old and new antiinfective agents.