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Triazole antifungal Pregnancy: Should not be used in standard doses/short-term treatment in pregnancy unless clearly necessary; high-dose and/or prolonged regimens should not be used except for potentially life-threatening infections. Observational studies suggest increased risk of spontaneous abortion and a small increased risk of musculoskeletal malformations. Breast-feeding may be maintained after a single 150 mg dose but is not recommended after repeated or high-dose use.

Fluconazole

Brand names: Diflucan

Fluconazole is a triazole antifungal used for candidal infections, including oropharyngeal, oesophageal, vaginal and invasive candidiasis, and for cryptococcal meningitis and prophylaxis in immunocompromised patients.

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: Dose depends on indication (e.g. genital candidiasis 150 mg single dose; invasive candidiasis 800 mg loading then 400 mg once daily; cryptococcal meningitis 400 mg loading then 200-400 mg once daily)
Route: Oral (dose is the same for oral and IV administration)
Frequency: Once daily (except single-dose and weekly regimens below)
Max: In life-threatening infections the daily dose can be increased to 800 mg
Dose should be based on nature and severity of infection. Cryptococcal meningitis: 400 mg on day 1, then 200-400 mg once daily, usually 6-8 weeks (may increase to 800 mg daily in life-threatening infection); maintenance to prevent relapse 200 mg daily. Coccidioidomycosis: 200-400 mg once daily. Invasive candidiasis: 800 mg on day 1, then 400 mg once daily. Oropharyngeal candidiasis: 200-400 mg on day 1, then 100-200 mg once daily for 7-21 days. Oesophageal candidiasis: 200-400 mg on day 1, then 100-200 mg once daily for 14-30 days. Acute vaginal candidiasis / candidal balanitis: 150 mg single dose. Recurrent vaginal candidiasis: 150 mg every third day for 3 doses (days 1, 4, 7), then 150 mg once weekly for 6 months. Dermatomycosis (tinea pedis/corporis/cruris): 150 mg once weekly or 50 mg once daily for 2-4 weeks. Tinea versicolor: 300-400 mg once weekly for 1-3 weeks. Onychomycosis: 150 mg once weekly. Prophylaxis in prolonged neutropenia: 200-400 mg once daily. Elderly: adjust to renal function.

Paediatric dose

Dose: 6 mg/kg
Route: Oral (administered as a single daily dose)
Frequency: Once daily
Max: A maximum dose of 400 mg daily should not be exceeded in paediatric population
Infants, toddlers and children (28 days to 11 years). Mucosal candidiasis: initial dose 6 mg/kg, then 3 mg/kg once daily. Invasive candidiasis / cryptococcal meningitis: 6 to 12 mg/kg once daily depending on severity. Maintenance to prevent relapse of cryptococcal meningitis: 6 mg/kg once daily. Prophylaxis of Candida in immunocompromised patients: 3 to 12 mg/kg once daily. Term newborn infants (0-27 days) and adolescents (12-17 years) dose per SPC/weight and pubertal development. Clinician to verify all paediatric doses against a children's formulary.

Dose adjustments

Renal

No adjustment for single-dose therapy. For multiple doses: give an initial dose of 50-400 mg based on indication, then for creatinine clearance <=50 ml/min (no haemodialysis) use 50% of the recommended dose; creatinine clearance >50 ml/min use 100%. Haemodialysis patients: 100% of the recommended dose after each session, reduced dose per creatinine clearance on non-dialysis days.

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

Infants, toddlers and children (28 days to 11 years). Mucosal candidiasis: initial dose 6 mg/kg, then 3 mg/kg once daily. Invasive candidiasis / cryptococcal meningitis: 6 to 12 mg/kg once daily depending on severity. Maintenance to prevent relapse of cryptococcal meningitis: 6 mg/kg once daily. Prophylaxis of Candida in immunocompromised patients: 3 to 12 mg/kg once daily. Term newborn infants (0-27 days) and adolescents (12-17 years) dose per SPC/weight and pubertal development. Clinician to verify all paediatric doses against a children's formulary.

Verify in a children's formulary

Contraindications

  • Hypersensitivity to the active substance, to related azole substances, or to any of the excipients
  • Co-administration of terfenadine in patients receiving fluconazole at multiple doses of 400 mg/day or higher
  • Co-administration of other medicinal products known to prolong the QT interval and metabolised via CYP3A4 (e.g. cisapride, astemizole, pimozide, quinidine, erythromycin)

Side effects

  • Headache (common)
  • Abdominal pain, vomiting, diarrhoea, nausea (common)
  • Rash (common); drug eruption, urticaria, pruritus (uncommon)
  • Alanine aminotransferase / aspartate aminotransferase / blood alkaline phosphatase increased (common)
  • Torsade de pointes and QT prolongation (rare); anaphylaxis (uncommon)

Interactions

  • Terfenadine (contraindicated at fluconazole doses >=400 mg/day)
  • QT-prolonging CYP3A4 substrates - cisapride, astemizole, pimozide, quinidine, erythromycin (contraindicated)
  • Oral contraceptives (ethinyl estradiol / levonorgestrel) - modest increases in exposure reported
  • Amiodarone - QT prolongation may be amplified

Clinical monograph

How it works

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

Prescribing in practice

  • Fluconazole prolongs the QT interval and is a potent enzyme inhibitor, so it must not be co-administered with other QT-prolonging or CYP-interacting drugs that risk serious arrhythmia, and is teratogenic at high doses in pregnancy.
  • As a CYP2C9, CYP2C19 and CYP3A4 inhibitor it raises levels of many drugs including warfarin, phenytoin and certain statins, requiring review of co-medication.
  • It is renally cleared, so the dose should be reduced in significant renal impairment.

Monitoring

Monitor liver function during prolonged therapy and review electrolytes and concurrent QT-prolonging or interacting medicines, with INR checks if taken with warfarin.

Counselling the patient

  • Report any palpitations, fainting, or signs of liver problems such as jaundice or persistent nausea.
  • Tell your prescriber about all other medicines, as fluconazole interacts with many drugs.
  • Avoid becoming pregnant during treatment unless your doctor advises it is necessary.

Evidence & guidelines

Fluconazole is established in NICE and specialist antifungal guidance for candidal and cryptococcal infections, with MHRA warnings on QT prolongation and pregnancy risk.

Reference: IDSA Candidiasis Guidelines 2016; PHE 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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