This review drew on studies and international guidelines up to November 2025 to set out where antifungal therapeutic drug monitoring is supported and where target ranges still disagree.
The case is strongest for voriconazole and posaconazole. Both show wide variation in exposure between patients, and their trough targets are well established and linked to clinical outcomes, so routine monitoring is supported. For isavuconazole, routine monitoring is not universally advised, but it may help in critically ill, paediatric and obese patients and in those on extracorporeal therapies such as ECMO or renal replacement. Echinocandins and amphotericin B are not routinely monitored, because exposure–response data are limited, though there are situations where levels may help. Differences in targets, assay methods and sampling practice explain much of the inconsistency between centres.
This is a narrative synthesis rather than new outcome data, and it argues for harmonised targets rather than setting them. Its practical value is the ranking: voriconazole and posaconazole levels should be routine; isavuconazole levels are for selected patients; others need a specific reason.
- Check voriconazole and posaconazole trough levels routinely, using your laboratory's target ranges.
- Consider isavuconazole levels in critically ill, paediatric or obese patients and those on ECMO or renal replacement therapy.
- Echinocandin and amphotericin B levels are not routinely needed.
- Take troughs at steady state, and repeat after dose changes or new interacting drugs.
- Review azole interactions, especially with rifampicin, tacrolimus and many antiretrovirals, when interpreting levels.
Why it matters
Variable exposure means a standard azole dose can leave some patients underdosed and others toxic.
Don't overread it
The review does not set harmonised targets; it argues they are still needed.
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