Isavuconazole is an antifungal medicine used to treat serious, invasive fungal infections. It belongs to a class of medicines called triazole antifungals, and is given as isavuconazonium sulfate, a prodrug that is converted to active isavuconazole in the body. It is a prescription-only medicine, notable for being available in both oral and intravenous forms with equivalent dosing.

• Therapeutic Class: Systemic antifungal medicine.

• Pharmacological Class: Triazole antifungal (ergosterol synthesis inhibitor).

• Drug Family: Broad-spectrum azole antifungals.

• ATC Classification: J02AC05 (Isavuconazole).

Approved: Invasive aspergillosis (a serious fungal lung/systemic infection) and invasive mucormycosis (a serious, often rapidly progressive fungal infection), in patients 18 years and older (with some regional approvals in younger patients).

Commonly used for: Immunocompromised patients — such as those with blood cancers, stem cell or organ transplant recipients, or patients on long-term high-dose steroids — who develop these serious invasive fungal infections.

Off-label use (only under medical guidance): Sometimes used as antifungal prophylaxis in high-risk patients (e.g., during intensive chemotherapy or stem cell transplant), under specialist guidance.

● Oral capsules: 74.5 mg isavuconazonium sulfate (equivalent to 40 mg isavuconazole).

● Injection (intravenous, lyophilized powder for reconstitution): 372 mg isavuconazonium sulfate (equivalent to 200 mg isavuconazole) per vial.

Isavuconazole blocks an enzyme fungi need to produce ergosterol, an essential component of the fungal cell membrane. Without adequate ergosterol, the fungal cell membrane becomes unstable, which stops the fungus from growing and helps the body clear the infection.

Standard loading dose: 372 mg (equivalent to 200 mg isavuconazole) given orally or intravenously every 8 hours for the first 6 doses (48 hours).

Standard maintenance dose: 372 mg (equivalent to 200 mg isavuconazole) given orally or intravenously once daily, starting 12 to 24 hours after the last loading dose, continued for the duration of treatment as determined by the treating specialist.

Route: Oral (capsules, with or without food) or intravenous infusion (over at least 1 hour, using an inline filter); no dose adjustment is needed when switching between oral and IV forms, given the high oral bioavailability.

Missed dose: Take as soon as remembered; contact the treating team for guidance if a dose is significantly delayed, given the importance of consistent dosing in serious fungal infections.

Overdose: May worsen known side effects such as liver enzyme changes or gastrointestinal symptoms; requires medical attention.

• Common: Nausea, vomiting, diarrhoea, headache, elevated liver enzymes, low blood potassium, constipation, and shortness of breath.

• Serious: Liver toxicity (including rare severe hepatic reactions), infusion-related reactions (with the IV form), and severe allergic/hypersensitivity reactions.

• Emergency symptoms: Yellowing of the skin/eyes, severe abdominal pain, signs of a severe allergic reaction (swelling of the face/throat, difficulty breathing), or a very slow or irregular heartbeat.

• Recovery advice: Regular liver function monitoring allows the treating team to catch and manage liver-related changes early; unlike many other azole antifungals, isavuconazole tends to shorten rather than prolong the heart's QT interval.

• Pregnancy: Used only if clearly needed, as safety data are limited and animal studies have shown potential risk.

• Breastfeeding: Discussed with the treating doctor given limited safety data.

• Liver disease: No dose adjustment needed in mild to moderate impairment (Child-Pugh A and B); used with caution and liver function monitoring in severe impairment (Child-Pugh C).

• Kidney disease: No dose adjustment needed across mild, moderate, or severe renal impairment.

• Elderly: No dose adjustment needed based on age alone; used with routine monitoring.

• Children: Not established for use in children under 18 in the primary approved indications, though pediatric studies and some regional approvals exist.

● Strong CYP3A4 inhibitors (e.g., ketoconazole, certain HIV protease inhibitors): significantly increase isavuconazole levels; combined use is generally avoided.

● Strong CYP3A4 inducers (e.g., rifampin, carbamazepine, long-acting barbiturates): significantly reduce isavuconazole levels and effectiveness; combined use is generally avoided.

● Sensitive CYP3A substrates with a narrow therapeutic index (e.g., cyclosporine, tacrolimus, sirolimus, certain ergot derivatives): isavuconazole can increase their levels, requiring dose reduction of those medicines.

● Other QT-affecting medicines: while isavuconazole shortens rather than prolongs QT, patients on QT-prolonging drugs may still warrant caution/consultation given the unique QT-shortening mechanism.

● Liver function tests before starting and periodically during treatment.

● Electrolyte levels (potassium) periodically.

● Clinical and radiological assessment of the fungal infection to monitor treatment response.

● Monitoring for infusion-related reactions during IV administration.

Voriconazole, Posaconazole (other triazole antifungals, different QT and interaction profiles), Amphotericin B (a different antifungal class, used especially in mucormycosis and certain resistant infections).

Generally used as a standalone antifungal; in select severe or refractory cases, combination antifungal therapy may be considered under specialist infectious disease guidance, though this is not the standard approach.

● Invasive Fungal Infection Treatments

● Triazole Antifungals

● Immunocompromised Patient Supportive Care

1. What Is Fungal Acne Symptoms, Causes, and Treatment

2. Top 4 Treatment Of Fungal Infections Of The Skin

1. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/207500s016,207501s016lbl.pdf

2. https://reference.medscape.com/drug/cresemba-isavuconazole-isavuconazonium-sulfate-999988

The information on this page is for educational purposes only and is not a substitute for medical advice. Please consult your doctor to know if this treatment is appropriate for your condition.