This review in Therapeutic Drug Monitoring surveyed the literature and international guidelines to November 2025 to support harmonised therapeutic ranges for antifungals.
It finds robust support for routine trough monitoring of voriconazole and posaconazole, both of which have high pharmacokinetic variability and trough targets linked to clinical outcomes. For isavuconazole, routine monitoring is not universally recommended but may help in critically ill, paediatric and obese patients and those on extracorporeal therapies. Routine monitoring of echinocandins and amphotericin B is not currently recommended because exposure-response data are limited. Targets, assays and pre-analytical handling still vary between centres.
Voriconazole in particular shows wide variation, partly from CYP2C19 genotype — relevant in South Asian populations, where poor-metaboliser variants are relatively common — and from interactions. Monitoring levels is how prescribers find the patients who are under- or over-exposed before treatment fails or toxicity appears.
- Measure voriconazole trough levels routinely within the first week of therapy.
- Measure posaconazole levels, particularly with the oral suspension or when absorption is uncertain.
- Consider isavuconazole levels in critically ill, paediatric, obese or ECMO and CRRT patients.
- Recheck levels after starting or stopping an interacting drug.
- Use the target range your laboratory reports, as targets vary between centres.
Why it matters
Fixed dosing of the variable triazoles leaves many patients outside the effective range without anyone knowing.
Don't overread it
Exact target ranges still differ across guidelines, and evidence is weaker for isavuconazole, echinocandins and amphotericin B.
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