Therapeutic Drug Monitoring: More Than Avoiding Toxicity

Therapeutic drug monitoring (TDM) is a clinical science centered around the quantification of drug concentrations in body fluids. To be considered candidates for TDM drugs must possess certain characteristics, including a narrow therapeutic index; in other words, to avoid toxicity at clinical doses. The relationship between dose and systemic concentration is particularly poor and unpredictable in special populations liable to different or dynamically changing pharmacokinetics. Antimicrobial use in the critical care setting has received special attention, where adequate concentrations for efficacy are especially pertinent. This chapter reviews recent evidence for TDM of established candidate drugs, aminoglycosides and vancomycin, and emerging evidence for beta-lactams, fluoroquinolones, linezolid, colistin and daptomycin, in the critically ill patient. The use of dose adaptation software for dose adjustment is discussed.