Antifungal susceptibility testing, pharmacokinetics and pharmacodynamics, and therapeutic drug monitoring: putting it together
Nathan P. Wiederhold
Fungus Testing Laboratory, Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, U.S.A
Abstract
Laboratory tests are often used by clinicians to help in the management of patients with invasive fungal infections. Two types of tests that are commonly used include in vitro susceptibility testing and therapeutic drug monitoring. Antifungal susceptibility testing is a phenotypic means used to determine if an organism cultured from a patient with an infection may be susceptible or resistant to a particular drug or group of drugs. The results of susceptibility testing are most useful when interpretive breakpoints are available. Therapeutic drug monitoring is used to measure concentrations of antifungals within biological fluids, such as serum or plasma, and then applying pharmacokinetic principles to individualize a dosing regimen. For agents that have narrow therapeutic windows, the goal is to optimize clinical responses while avoiding concentration-dependent toxicities. Pharmacokinetic / pharmacodynamic studies are used to link a pharmacokinetic parameter with a pharmacodynamic measure of drug activity. The purpose of this review is to provide an overview of in vitro susceptibility testing, therapeutic drug monitoring, and pharmacokinetic / pharmacodynamic analysis and how these are used to inform decisions regarding individual patient care as well as in designing dosing regimens and antifungal breakpoints.
Open Access
Cite this article:
Wiederhold NP, 2025. Antifungal susceptibility testing, pharmacokinetics and pharmacodynamics, and therapeutic drug monitoring: putting it together. One Health Mycology 2(1), 42-52
ISSN: 3050-4627
doi.org/10.63049/OHM.25.21.3
Keywords:
Susceptibility; resistance; breakpoints; antifungals; therapeutic drug monitoring; pharmacokinetics / pharmacodynamics
Article highlights:
- Comparing and contrasting CLSI and EUCAST antifungal susceptibility testing methods and breakpoints.
- How pharmacokinetic / pharmacodynamic parameters are used to establish breakpoints and optimize dosing regimens.
- Use of therapeutic drug monitoring for optimizing an individual patient’s treatment regimen.
#Correspondence:
wiederholdn@uthscsa.edu
Article info:
Received 6 March 2025
Revised 6 April 2025
Accepted 7 April 2025
Appeared online 17 April 2025
One Health Mycology 2(1): 42−52, 2025