[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Azole antifungals](https://durgical.com/en/pharmacology/classes/azole-antifungals/) › Ketoconazole [Pharmacology](https://durgical.com/en/pharmacology/) · [Azole antifungals](https://durgical.com/en/pharmacology/classes/azole-antifungals/) # Ketoconazole Imidazole antifungal. As a cream or shampoo it treats seborrhoeic dermatitis and tinea; by mouth it is a last resort because it harms the liver. Updated 2026-11-01 - Class: [Azole antifungals](https://durgical.com/en/pharmacology/classes/azole-antifungals/) - Enzyme: Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme) - ATC code: J02AB02 ✂**Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme)**Ketoconazole ⓘ The figure shows ketoconazole bound to human CYP51, the human counterpart of the fungal enzyme; ketoconazole's binding to human P450 enzymes explains part of its toxicity. **Target in 3D:** Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme). PDB structure 3LD6 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3LD6) · Drag to rotate · pinch to zoom ## Mechanism of action Ketoconazole blocks fungal lanosterol 14α-demethylase, so methylated sterols accumulate and ergosterol is depleted. Taken by mouth it also inhibits human steroid-making P450 enzymes, lowering testosterone and cortisol synthesis, and is a strong CYP3A4 inhibitor. - Ketoconazole blocks fungal CYP51 - Ergosterol is depleted and the membrane weakens - Orally it also blocks human steroid synthesis ## Pharmacokinetics **Absorption** A weak base that needs stomach acid to dissolve; antacids, H2 blockers and PPIs reduce absorption. **Distribution** Penetrates the CSF poorly, so it is not used for fungal meningitis. **Metabolism** Liver. ## Indications - Seborrhoeic dermatitis and dandruff (cream, shampoo). [Seborrheic dermatitis →](https://durgical.com/en/conditions/seborrheic-dermatitis/) - Pityriasis (tinea) versicolor (shampoo, cream). [Pityriasis versicolor →](https://durgical.com/en/conditions/pityriasis-versicolor/) - Tinea corporis, cruris and pedis (cream). [Dermatophytosis (tinea) and onychomycosis →](https://durgical.com/en/conditions/dermatophytosis-and-onychomycosis/) - Oral form only when other therapy has failed or is not tolerated: paracoccidioidomycosis, histoplasmosis, blastomycosis, coccidioidomycosis, chromomycosis. [Paracoccidioidomycosis →](https://durgical.com/en/conditions/paracoccidioidomycosis/) ## Adverse effects ### Common - Topical: irritation, itching or stinging where applied - Oral: nausea, vomiting, diarrhoea, abdominal pain, taste changes - Oral: gynaecomastia and lower testosterone ### Serious (rare, important) - Oral: serious hepatotoxicity, sometimes fatal or requiring liver transplant, even without risk factors - Oral: QT prolongation and life-threatening arrhythmias through interactions - Oral: adrenal insufficiency ## Contraindications - Oral: acute or chronic liver disease - Oral: dofetilide, quinidine, pimozide, cisapride, methadone, disopyramide, dronedarone, ranolazine, simvastatin, lovastatin, oral midazolam, triazolam, ergot alkaloids, among others - Oral: not for onychomycosis, skin dermatophyte or Candida infections ## Key interactions **QT-prolonging CYP3A4 substrates (dofetilide, quinidine, pimozide, methadone)** Contraindicated with the oral form: torsade de pointes. **Antacids, H2 blockers and PPIs** Reduce absorption of the tablets; antacids are separated in time. **Simvastatin and lovastatin** Contraindicated with the oral form: rhabdomyolysis. ## What is monitored - Oral: liver tests before and during treatment - Oral: adrenal function in patients at risk or under stress - Topical: response of the skin lesions ## Administration and safety - Check which form is ordered: topical forms are common and safe; oral tablets are restricted. - Separate antacids from the tablets (at least an hour before or two hours after). - Shampoo and cream are for external use only. ## Nursing care - With oral ketoconazole, teach the signs of liver injury and to report them at once. - Ask about palpitations or fainting; review all medicines for contraindicated combinations. - With topical use, report spreading redness, blisters or swelling. ## Pregnancy and breastfeeding Oral ketoconazole was teratogenic in rats; used in pregnancy only if the benefit justifies the risk. ## Memory aid «KETO kills the liver and the hormones»: oral form blocks testosterone and cortisol; keep it on the skin and scalp. ## Test yourself Think of the answer, then tap the question to see it. ## Why is oral ketoconazole no longer used for nail or skin fungus? Its risks (serious hepatotoxicity, QT interactions, adrenal insufficiency) outweigh benefits when safer options exist. ## Why can ketoconazole cause gynaecomastia? It inhibits human P450 enzymes that make steroids, lowering testosterone. ## What is the most common use of ketoconazole today? Topical: cream or shampoo for seborrhoeic dermatitis, dandruff, pityriasis versicolor and tinea. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/ketoconazole/) ## Related drugs - [Itraconazole](https://durgical.com/en/pharmacology/itraconazole/) - [Clotrimazole](https://durgical.com/en/pharmacology/clotrimazole/) - [Miconazole](https://durgical.com/en/pharmacology/miconazole/) ## Related conditions - [Seborrheic dermatitis](https://durgical.com/en/conditions/seborrheic-dermatitis/) - [Pityriasis versicolor](https://durgical.com/en/conditions/pityriasis-versicolor/) - [Dermatophytosis (tinea) and onychomycosis](https://durgical.com/en/conditions/dermatophytosis-and-onychomycosis/) - [Paracoccidioidomycosis](https://durgical.com/en/conditions/paracoccidioidomycosis/) [← Back to the class: Azole antifungals](https://durgical.com/en/pharmacology/classes/azole-antifungals/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - KETOCONAZOLE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6d4be760-c723-4f54-a854-12c61cf91703) (DailyMed (U.S. National Library of Medicine), 2026); [Ketoconazole Topical: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a605014.html) (MedlinePlus (U.S. National Library of Medicine), 2016); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 61 (McGraw Hill, 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/ketoconazole/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/ketoconazole/