Therapeutic Drug Monitoring (TDM) is the art of measuring the levels of a
therapeutic agent in body fluids, most commonly plasma, and interpreting the results in
order to adjust dosing such that therapeutic benefit is maximized and toxic effects are
prevented. With respect to antibiotics, TDM was traditionally viewed as a method to
curtail the side effects of agents with narrow therapeutic indices. However, with
improved understanding of pharmacokinetic differences in various patient populations,
TDM is evolving to a method by which to ensure adequate benefit in patients whose
pharmacokinetic status is in question. Moreover, the ever-increasing surge in
antimicrobial-resistant organisms is calling for this practice once more, this time to
ensure that drug concentrations are maintained sufficiently large in order to combat
infections with such organisms. This book chapter details the use of TDM in different
patient populations and for different antimicrobials, with emphasis on how reference
PK/PD parameters and drug levels are determined.
Keywords: Aminoglycosides, Antimicrobial Agents, Beta Lactams, Critically Ill
Patients, Fluoroquinolones, Glycopeptides, Linezolid, Minimum Inhibitory
Concentration, Pharmacodynamics, Pharmacokinetics, PK/PD index, Therapeutic
Drug Monitoring, Vancomycin.
