What is the role of therapeutic drug monitoring in antifungal therapy?

Despite an expanding number of therapeutic options for treating invasive fungal infection (IFI), the mortality rate from these infections remains high. Many risk factors for poor outcome from IFI (eg, the compromised immune status of the host) are not modifiable by the treating clinician. Thus, elevated interest exists in any modifiable factor that might improve outcome. Many of the new antifungal agents have marked variability in drug concentration based on either inconsistent absorption or elimination, leading to very wide interpatient variability. Many agents also have a narrow therapeutic index, meaning a small range between drug levels too low to achieve the desired clinical benefit and high enough to produce unwanted or toxic effects. Therefore, therapeutic drug monitoring is useful to maximize efficacy while minimizing drug toxicity of some antifungal agents.