A review in Therapeutic Drug Monitoring gathered literature and guidelines up to November 2025 to clarify where antifungal drug monitoring is justified and which targets to use.
Evidence is robust for routine trough monitoring of voriconazole and posaconazole: both show wide variation between patients, many interactions, and trough levels linked to outcomes. Isavuconazole does not need routine monitoring, but may benefit selected high-risk patients — the critically ill, children, the obese and those on extracorporeal therapies such as ECMO or continuous renal replacement. Echinocandins and amphotericin B lack the exposure-response data to support routine monitoring, though some situations may justify it.
The authors note that inconsistent targets, laboratory methods and sampling practices still hold back implementation. For a prescriber, the clear message is not to give voriconazole or posaconazole without a level, and to think about isavuconazole levels in the patients most likely to fall outside the usual range.
- Check a voriconazole trough after about five days and after any dose or interacting drug change
- Check posaconazole troughs, particularly with the suspension and in patients with diarrhoea or mucositis
- Consider isavuconazole levels in critically ill, paediatric or obese patients and those on ECMO or CRRT
- Review interacting drugs, especially inducers and CYP3A substrates, whenever an azole is started
- Use your laboratory's stated target range, since targets still vary between guidelines
Why it matters
Azole exposure varies widely between patients, and both under- and over-exposure carry clinical consequences.
Don't overread it
The review supports monitoring but notes that target ranges are not yet fully harmonised across guidelines.
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