Isavuconazole

How it works

It inhibits fungal cytochrome P450 lanosterol 14-alpha-demethylase, blocking ergosterol biosynthesis and compromising the fungal cell membrane.

Prescribing in practice

• Unlike most azoles isavuconazole shortens the QT interval and is contraindicated in familial short QT syndrome, while remaining a clinically significant CYP3A4 interacting drug.
• It is contraindicated with strong CYP3A4 inducers or inhibitors such as rifampicin and high-dose ritonavir, which alter exposure substantially.
• It requires caution and monitoring in hepatic impairment, where it has not been studied in severe disease.

Monitoring

Monitor liver function during therapy and review concurrent medicines for CYP3A4 interactions; routine therapeutic drug monitoring is less commonly required than with some other triazoles.

Counselling the patient

• Tell your prescriber about all other medicines, as isavuconazole has important drug interactions.
• Report signs of liver problems such as jaundice, dark urine or persistent nausea.
• Mention any family history of a short QT heart rhythm condition.

Evidence & guidelines

Isavuconazole is recommended in specialist antifungal guidance as a treatment option for invasive aspergillosis and mucormycosis, supported by its registration trials.