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Antifungal — Oral Candidiasis

Fluconazole

Brand names: Diflucan

Fluconazole is a triazole antifungal used for candidal infections (including thrush) and some systemic fungal infections.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

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.

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. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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