Triazole Antifungal Pregnancy: Must not be used during pregnancy unless the benefit to the mother clearly outweighs the potential risk to the foetus (animal reproductive toxicity; human risk unknown). Women of child-bearing potential must use effective contraception. Breast-feeding must be stopped on initiation of treatment.

Voriconazole

Brand names: Vfend

Voriconazole is a triazole antifungal used for invasive aspergillosis and other serious fungal infections.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Loading (first 24 h): IV 6 mg/kg every 12 hours, or oral 400 mg every 12 hours (patients 40 kg and above) / 200 mg every 12 hours (less than 40 kg). Maintenance (after first 24 h): IV 4 mg/kg twice daily, or oral 200 mg twice daily (40 kg and above) / 100 mg twice daily (less than 40 kg)

Route: Intravenous infusion (maximum rate 3 mg/kg per hour over 1 to 3 hours) or oral

Frequency: every 12 hours (loading, first 24 hours); twice daily (maintenance)

Applies to patients aged 15 years and older. High oral bioavailability (96%) - switching between IV and oral is appropriate when clinically indicated. Dose adjustment: if IV 4 mg/kg twice daily is not tolerated, reduce to 3 mg/kg twice daily; if response is inadequate, oral maintenance may be increased to 300 mg twice daily (150 mg twice daily for patients less than 40 kg), then reduced in 50 mg steps if not tolerated. Duration should be as short as possible; more than 180 days requires careful benefit-risk assessment. Prophylaxis (transplant): same regimen as treatment for the age group; start on day of transplant, up to 100 (and up to 180) days. Elderly: no dose adjustment necessary. Hepatic impairment (mild-moderate, Child-Pugh A/B): use the standard loading dose but halve the maintenance dose. Coadministration: with rifabutin or phenytoin increase IV maintenance to 5 mg/kg twice daily; with efavirenz increase voriconazole to 400 mg every 12 hours and reduce efavirenz to 300 mg once daily. Correct hypokalaemia/hypomagnesaemia/hypocalcaemia before and during therapy.

Paediatric dose

Dose: 9 mg/kg

Route: Oral - children 2 to under 12 years, and young adolescents 12 to 14 years weighing less than 50 kg (verify against a children's formulary)

Frequency: twice daily (maintenance, after first 24 hours)

Max: 350 mg twice daily (oral maintenance)

SPC paediatric regimen for children 2 to under 12 years and low-weight adolescents (12 to 14 years, under 50 kg): IV loading 9 mg/kg every 12 hours for the first 24 hours; then IV maintenance 8 mg/kg twice daily OR oral maintenance 9 mg/kg twice daily (maximum 350 mg twice daily). Oral loading is not recommended. Initiate with the IV regimen; use oral only after significant clinical improvement. An 8 mg/kg IV dose gives voriconazole exposure about 2-fold higher than a 9 mg/kg oral dose. Adolescents 12 to 14 years and 50 kg or more, and 15 to 17 years regardless of body weight: dose as adults. Not studied in children under 2 years or with hepatic/renal insufficiency. Verify against a children's formulary.

Dose adjustments

Renal

Moderate to severe renal impairment (creatinine clearance less than 50 mL/min): use oral voriconazole because the IV vehicle (SBECD) accumulates; monitor serum creatinine closely. A 4-hour haemodialysis session does not remove enough voriconazole to warrant dose adjustment.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

• Dosage in Adults ( 2.3 ) Infection Loading Dose Maintenance Dose Intravenous infusion Intravenous infusion Oral tablets Oral suspension Invasive Aspergillosis 6 mg/kg every 12 hours for the first 24 hours 4 mg/kg every 12 hours 200 mg every 12 hours 5 mL every 12 hours Candidemia in nonneutropenics and other deep tissue Candida infections 3–4 mg/kg every 12 hours 200 mg every 12 hours 5 mL every 12 hours Scedosporiosis and Fusariosis 4 mg/kg every 12 hours 200 mg every 12 hours 5 mL every 12 hours Esophageal Candidiasis Not Evaluated Not Evaluated 200 mg every 12 hours 5 mL every 12 hours o Adult patients weighing less than 40 kg: oral maintenance dose 100 mg or 150 mg every 12 hours o …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-03-20. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to voriconazole or any excipient
Coadministration with CYP3A4-dependent drugs causing serious reactions: terfenadine, astemizole, cisapride, pimozide, lurasidone, quinidine, ivabradine, ergot alkaloids (ergotamine, dihydroergotamine), sirolimus, naloxegol, tolvaptan, finerenone, venetoclax (at initiation/titration)
Coadministration with strong CYP3A4 inducers that reduce voriconazole levels: rifampicin, carbamazepine, long-acting barbiturates (e.g. phenobarbital), St John's Wort
Efavirenz at 400 mg once daily or higher (with standard-dose voriconazole)
High-dose ritonavir (400 mg and above twice daily)

Side effects

Visual impairment / visual disturbances
Pyrexia (fever)
Rash
Nausea and vomiting; diarrhoea
Abnormal liver function tests

Interactions

Strong CYP3A4 inducers (rifampicin, rifabutin, carbamazepine, phenobarbital, St John's Wort) - significantly reduce voriconazole levels (contraindicated)
Efavirenz and ritonavir - dose-dependent contraindication/adjustment
Phenytoin or rifabutin - increase voriconazole IV maintenance to 5 mg/kg twice daily if coadministered
CYP3A4 substrates (sirolimus, ergot alkaloids, pimozide, quinidine and others) - contraindicated
Voriconazole is a strong inhibitor of CYP3A4 and inhibits CYP2C19/CYP2C9 - may raise plasma levels of their substrates

Clinical monograph

How it works

It inhibits fungal cytochrome P450-dependent 14-alpha-demethylase, blocking ergosterol synthesis and disrupting the fungal cell membrane.

Prescribing in practice

A potent CYP450 inhibitor (CYP2C19, CYP2C9, CYP3A4) with many serious, sometimes contraindicated, drug interactions — screen co-medication carefully before starting.
Hepatotoxicity, QT prolongation and visual disturbances can occur; long-term use carries a risk of phototoxicity and skin malignancy.
Therapeutic drug monitoring of plasma levels is used to guide dosing, given wide pharmacokinetic variability.

Monitoring

Monitor liver function before and during treatment, check electrolytes and correct potassium/magnesium given QT risk, and use plasma trough levels to optimise efficacy and limit toxicity. Review skin regularly with prolonged therapy.

Counselling the patient

Visual changes (blurring, altered colour or brightness perception) are common, usually transient and reversible — avoid driving or operating machinery if affected.
Avoid direct sunlight and use effective sun protection, as the skin becomes very sensitive and long-term use raises skin-cancer risk; report any new or changing skin lesion.
Report yellowing of the skin or eyes, dark urine or persistent nausea, which may signal liver problems.

Evidence & guidelines

First-line for invasive aspergillosis, having shown improved survival over conventional amphotericin B; supported by UK and international antifungal guidance.

Reference: ESCMID/ECMM/ERS Aspergillosis Guidelines 2017; IDSA Aspergillosis Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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