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Antifungal — Oral Candidiasis 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 thrush) and some systemic 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: Oropharyngeal candidiasis: 200-400 mg on day 1, then 100-200 mg once daily; Oesophageal candidiasis: 200-400 mg on day 1, then 100-200 mg once daily
Route: Oral (dose is the same for oral and IV administration)
Frequency: Once daily (see indication-specific durations)
Max: In life-threatening infections the daily dose can be increased to 800 mg
ENT-relevant mucosal candidiasis regimens shown in dose. Oropharyngeal candidiasis: loading 200-400 mg on day 1, then 100-200 mg once daily for 7-21 days (until remission; longer if severely immunocompromised). Oesophageal candidiasis: loading 200-400 mg on day 1, then 100-200 mg once daily for 14-30 days. Prevention of relapse of mucosal candidiasis in HIV: 100-200 mg once daily or 200 mg three times per week. Other indications per full SPC (invasive candidiasis 800 mg day 1 then 400 mg once daily; cryptococcal meningitis 400 mg day 1 then 200-400 mg once daily; acute vaginal candidiasis 150 mg single dose). 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 (oropharyngeal/oesophageal - ENT-relevant): 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. Prophylaxis of Candida in immunocompromised patients: 3 to 12 mg/kg once daily. Adolescents (12-17 years) dose per 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 (oropharyngeal/oesophageal - ENT-relevant): 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. Prophylaxis of Candida in immunocompromised patients: 3 to 12 mg/kg once daily. Adolescents (12-17 years) dose per weight and pubertal development. Clinician to verify all paediatric doses against a children's formulary.

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Dosage and Administration in Adults: Single Dose Vaginal candidiasis: The recommended dosage of fluconazole for vaginal candidiasis is 150 mg as a single oral dose. Multiple Dose SINCE ORAL ABSORPTION IS RAPID AND ALMOST COMPLETE, THE DAILY DOSE OF FLUCONAZOLE IS THE SAME FOR ORAL AND INTRAVENOUS ADMINISTRATION. In general, a loading dose of twice the daily dose is recommended on the first day of therapy to result in plasma concentrations close to steady-state by the second day of therapy. The daily dose of fluconazole for the treatment of infections other than vaginal candidiasis should be based on the infecting organism and the patient’s response to therapy. …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-11-17. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

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 (14α-demethylase), impairing ergosterol synthesis and the fungal cell membrane.

Prescribing in practice

  • It inhibits human CYP enzymes (notably CYP2C9 and CYP3A4), interacting with many drugs — e.g. increasing the effect of warfarin and the myopathy risk with some statins.
  • It can prolong the QT interval and cause hepatotoxicity; reduce the dose in renal impairment for multiple-dose courses.
  • Higher or prolonged doses are teratogenic — avoid in pregnancy other than a single low dose for thrush where the benefit outweighs the risk.

Monitoring

For longer courses consider liver function; review interacting drugs (e.g. INR with warfarin) and QT risk.

Counselling the patient

  • Tell your clinician about all other medicines, as it interacts with many.
  • Report yellowing of the skin or eyes.
  • A single-dose treatment is common for thrush.

Evidence & guidelines

First-line for many candidal infections, with important drug-interaction, QT and pregnancy cautions.

Reference: BSAC Oral Candidiasis Guidelines; NICE CKS Oral Candidiasis; 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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