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# Isavuconazole

Triazole for invasive aspergillosis and mucormycosis, given as the prodrug isavuconazonium. Unlike other azoles it shortens the QT interval.

Updated 2026-11-01

- Class: [Azole antifungals](https://durgical.com/en/pharmacology/classes/azole-antifungals/)
- Enzyme: Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme)
- ATC code: J02AC05

Also called: isavuconazonium sulfate (prodrug)

✂**Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme)**Isavuconazole

ⓘ The figure shows isavuconazole bound to CYP51 of the amoeba Acanthamoeba castellanii, the same sterol-demethylase site that the drug blocks in fungi.

**Target in 3D:** Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme). PDB structure 6UX0 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/6UX0) · Drag to rotate · pinch to zoom

## Mechanism of action

Isavuconazonium is rapidly hydrolysed in the blood to isavuconazole, which inhibits fungal lanosterol 14α-demethylase like other triazoles. Its broad spectrum includes Aspergillus and the Mucorales. It is both a substrate and an inhibitor of CYP3A4.

- The prodrug isavuconazonium becomes isavuconazole
- Isavuconazole blocks fungal CYP51
- Aspergillus and Mucorales stop growing

## Pharmacokinetics

**Absorption**
Highly bioavailable by mouth; oral and intravenous forms are available, and the intravenous form contains no cyclodextrin.

**Distribution**
Over 99% protein-bound.

**Metabolism**
Liver, mainly CYP3A4 and CYP3A5; no dose change for kidney impairment.

**Half-life**
Very long, several days.

## Indications

- Invasive aspergillosis. [Aspergillosis →](https://durgical.com/en/conditions/aspergillosis/)
- Invasive mucormycosis.

## Adverse effects

### Common

- Nausea, vomiting, diarrhoea, constipation
- Fever, headache, cough
- Low potassium

### Serious (rare, important)

- Allergic reactions, including swelling and breathing difficulty
- Liver injury (nausea, jaundice, extreme tiredness)
- Fast or irregular heartbeat, dizziness or fainting

## Contraindications

- Familial short QT syndrome
- Allergy to isavuconazonium or other azoles
- Use with St John's wort

## Key interactions

**Strong CYP3A4 inhibitors (for example ketoconazole)**
Isavuconazole exposure rises several-fold.

**Rifampicin and St John's wort**
Isavuconazole levels fall sharply and treatment may fail.

**Midazolam and sirolimus**
Their exposure increases.

## What is monitored

- Liver tests
- Potassium
- Heart rhythm in patients with arrhythmia risk

## Administration and safety

- Capsules are swallowed whole: not opened, chewed, dissolved or crushed.
- Doses are written as isavuconazonium sulfate or as isavuconazole: check which the order uses.
- Keep capsules in their blister with the desiccant until use.

## Nursing care

- Ask about a family history of short QT syndrome, arrhythmias or low potassium before starting.
- Teach signs of liver injury and allergic reactions and to seek care at once.
- Women should avoid pregnancy during treatment and for 28 days after the last dose.

## Pregnancy and breastfeeding

May harm the fetus; pregnancy is avoided during treatment and for 28 days afterwards.

## Memory aid

«ISAvuconazole IS the Shortener»: the only azole that shortens QT, and it covers mucor.

## Test yourself

Think of the answer, then tap the question to see it.

## In which inherited condition is isavuconazole contraindicated, and why?

Familial short QT syndrome, because isavuconazole shortens the QT interval in a dose-related way.

## What is isavuconazonium?

The water-soluble prodrug, rapidly hydrolysed to the active isavuconazole.

## Besides aspergillosis, which serious mould infection is isavuconazole used for?

Invasive mucormycosis.

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## Related drugs

- [Voriconazole](https://durgical.com/en/pharmacology/voriconazole/)
- [Posaconazole](https://durgical.com/en/pharmacology/posaconazole/)
- [Amphotericin B](https://durgical.com/en/pharmacology/amphotericin-b/)

## Related conditions

- [Aspergillosis](https://durgical.com/en/conditions/aspergillosis/)

[← Back to the class: Azole antifungals](https://durgical.com/en/pharmacology/classes/azole-antifungals/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Isavuconazonium: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a615031.html) (MedlinePlus (U.S. National Library of Medicine), 2024); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 61 (McGraw Hill, 2023).

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Representative model, for educational purposes only.

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