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Imidazole antifungal

Ketoconazole

Brand names: Nizoral

Ketoconazole is an imidazole antifungal; topical formulations treat skin and scalp fungal infections, while oral ketoconazole is restricted to endogenous Cushing's syndrome owing to hepatotoxicity.

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.

Clinical monograph

How it works

It inhibits fungal cytochrome P450 14-alpha-demethylase to impair ergosterol synthesis; at higher systemic exposure it also inhibits steroidogenic enzymes, underpinning its use in Cushing's syndrome.

Prescribing in practice

  • Systemic ketoconazole carries a risk of serious, potentially fatal hepatotoxicity, so oral use for fungal infection is no longer authorised and it is reserved for Cushing's syndrome under specialist care.
  • It is a potent CYP3A4 inhibitor with numerous, sometimes serious, drug interactions including QT-prolonging agents.
  • Topical preparations have minimal systemic absorption and a favourable safety profile.

Monitoring

For oral therapy, monitor liver function before and regularly during treatment and review for drug interactions; topical use needs no routine monitoring.

Counselling the patient

  • For shampoo or cream, apply as directed and avoid contact with the eyes.
  • If taking tablets, report nausea, vomiting, abdominal pain, jaundice or dark urine immediately.
  • Tell your clinician about all other medicines because of important interactions.

Evidence & guidelines

The European medicines review withdrew authorisation of oral ketoconazole for fungal infections because hepatotoxicity risk outweighed benefit; see MHRA guidance.

Reference: MHRA Drug Safety Update 2013; 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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