Ketoconazole: Uses, Dosage & Safety Information

Ketoconazole is a prescription antifungal available as tablets, cream, shampoo and foam. The tablets are reserved for blastomycosis, coccidioidomycosis, histoplasmosis, chromomycosis and paracoccidioidomycosis in patients who failed or cannot tolerate other therapies. They are not indicated for nail, skin dermatophyte or Candida infections.

The clearest evidence of that is the label itself. The indications section of the tablets opens not with what they treat but with what they must not be used for — onychomycosis, cutaneous dermatophyte infections and Candida infections, the three commonest reasons anyone reaches for an antifungal.

What remains is a short list of deep systemic mycoses — blastomycosis, coccidioidomycosis, histoplasmosis, chromomycosis and paracoccidioidomycosis — and even those only in people who have failed or cannot tolerate other treatment. It is a second-line drug for uncommon infections, and the usual course runs about six months.

Meanwhile the same molecule is thoroughly ordinary on the skin. Ketoconazole shampoo, cream and foam are widely listed, some by prescription and some over the counter, and they carry none of the restrictions above, because a shampoo does not deliver a hepatotoxic dose to the liver.

Azoles that took over most of what oral ketoconazole used to do are covered separately: itraconazole, Sporanox, fluconazole and Vfend. For nail infection specifically, terbinafine is the drug that displaced it.

The usual adult starting dose is a single 200 mg tablet daily, and the recommended range of 200 to 400 mg a day is not exceeded.¹ That ceiling is not about efficacy: adrenal corticosteroid secretion falls at 400 mg and above.

Treatment continues until the active infection has subsided, which for a systemic mycosis usually means about six months. This is not a course anyone shortens on the basis of feeling better.

Liver function is monitored throughout, and the label directs that patients be told about the hepatotoxicity risk before starting rather than warned in general terms. Symptoms of liver injury are a reason to stop and be assessed, not to finish the week.

Topical forms follow their own instructions, which have nothing in common with the above: shampoo is applied to the scalp and rinsed, cream to the affected skin.

Substances that must not be combined with ketoconazole are listed once, in the interactions table below.

The side effects that matter on this page are the ones that changed the drug’s place in practice. They belong to the tablets; the shampoo and cream do not carry them.

The phrase in the label worth reading twice is that some patients who developed serious hepatotoxicity had no obvious risk factors for liver disease.¹ It means the people harmed could not have been identified in advance by screening, and that is what turned a widely used antifungal into a last-resort one.

Oral ketoconazole is indicated for blastomycosis, coccidioidomycosis, histoplasmosis, chromomycosis and paracoccidioidomycosis, in patients who have failed or who are intolerant to other therapies.¹ Laboratory as well as clinical documentation of infection is required before treatment starts, and the usual duration for a systemic infection is six months.

It is explicitly not for onychomycosis, cutaneous dermatophyte infections, or Candida infections — including thrush. Those uses were removed from the label, not merely discouraged, and the removal is stated in the boxed warning rather than buried in a precaution.

It is also not used for fungal meningitis, for a straightforwardly mechanical reason: the drug penetrates poorly into cerebrospinal fluid, so it cannot reach the infection.

Topical ketoconazole is a different proposition entirely. Shampoos at 1% and 2%, creams and a foam are used for seborrhoeic dermatitis, dandruff and skin fungal infections; some are prescription and some sit on the shelf. A flaking, itching scalp is not always dandruff: scalp psoriasis looks similar and does not respond to an antifungal, which is one reason the shampoo can seem to stop working. Nothing in the boxed warning applies to them.

For the infections that oral ketoconazole was once used for, the current answers are elsewhere: terbinafine or itraconazole for nails, fluconazole for Candida, nystatin for local mucosal disease.

Oral ketoconazole is prescription-only and second-line by licence. The Nizoral brand tablet is discontinued, so a prescription is filled with a generic 200 mg tablet.²

The topical forms span both categories: 1% shampoo and some creams are sold over the counter, while 2% shampoos, creams and the foam are prescription.³ The same active ingredient therefore sits on a supermarket shelf and behind a boxed warning at the same time, and the difference is the route, not the molecule.

What the restriction on the tablets means in practice is set out once, in Critical warnings for ketoconazole use, and the combinations that are ruled out are in Drug interactions with ketoconazole.

Hepatotoxicity

Serious hepatotoxicity, including cases with a fatal outcome or requiring liver transplantation, has occurred with oral ketoconazole, and some of those patients had no obvious risk factors for liver disease. Patients are informed of the risk by the prescriber and monitored closely during treatment.¹

The indication restriction is itself a warning

The boxed warning states that the tablets are not indicated for onychomycosis, cutaneous dermatophyte infections or Candida infections, and are used only where other effective therapy is unavailable or not tolerated and the benefits are judged to outweigh the risks. A prescription for oral ketoconazole for a nail or a skin patch is outside the label.

QT prolongation

Coadministration with several CYP3A4 substrates is contraindicated because the resulting plasma levels can prolong the QT interval and cause life-threatening ventricular dysrhythmias including torsades de pointes.

Adrenal function

Adrenal corticosteroid secretion falls at doses of 400 mg daily and above. The recommended range is not exceeded, and adrenal function is monitored in patients with adrenal insufficiency or borderline reserve, and during prolonged stress such as major surgery or intensive care.

Not for fungal meningitis

Ketoconazole penetrates poorly into cerebrospinal fluid and is not used for fungal meningitis.

Source: ³

The daily ceiling of 400 mg exists for an endocrine reason rather than an antifungal one. Ketoconazole reduces adrenal corticosteroid secretion at 400 mg and above, and the label notes this effect is not shared with the other azoles.¹ Adrenal function is monitored in anyone with borderline adrenal reserve and in anyone under prolonged physiological stress such as major surgery.

Ketoconazole is a potent inhibitor of CYP3A4, so it raises the plasma levels of drugs cleared by that enzyme. Where the affected drug prolongs the QT interval, the result can be a life-threatening arrhythmia, which is why several combinations are contraindicated outright rather than merely monitored.¹

Source:

This table is the only place on this page where interacting substances are listed. The contraindicated list is revised, so it is read from the current prescribing information rather than reproduced here in a form that could go stale.

Evidence scope

What has been reported to the FDA

As of the FAERS data cut of 30 July 2026, the FDA Adverse Event Reporting System held 17,284 reports naming ketoconazole, 9,357 of them coded serious — a serious-coded share of 54%.⁴

Who was this medicine studied in?

No FDA Drug Trials Snapshot exists for ketoconazole. Snapshots are published only for new molecular entities approved from January 2015 onward, and the tablet was approved on 12 June 1981.²

The evidence behind the current label is therefore old, and its most consequential part did not come from trials at all. The indication restriction rests on postmarketing hepatotoxicity: cases accumulated over decades of wide use, including in patients with no risk factors, and the label was rewritten around them. That is a different kind of evidence from a controlled trial, and it is the kind that only appears after a drug has been used widely enough for rare harm to become visible.¹

Who this is and is not appropriate for

Typically considered for: a person with blastomycosis, coccidioidomycosis, histoplasmosis, chromomycosis or paracoccidioidomycosis, whose infection is documented by laboratory testing, and who has failed or cannot tolerate other antifungal therapy.

Not appropriate for: anyone with a nail infection, a skin dermatophyte infection or Candida — all three are excluded by the boxed warning. Anyone with fungal meningitis, since the drug does not reach cerebrospinal fluid. And anyone taking dofetilide, quinidine, cisapride or pimozide, which are contraindicated combinations.

Needs a conversation first: anyone with existing liver disease or a reason for regular liver monitoring; anyone with adrenal insufficiency or borderline adrenal reserve, or facing major surgery; and anyone taking a medicine cleared by CYP3A4, which is a long list.

Where to go next

• Report a side effect: FDA MedWatch, or MHRA Yellow Card in the UK
• Full prescribing information, including the current contraindicated drug list: DailyMed
• Pregnancy-specific enquiries: MotherToBaby, or Bumps in the UK
• Dandruff and seborrhoeic dermatitis: the topical forms, which carry none of the restrictions on this page

1. FDA Prescribing Information — ketoconazole tablets 200 mg. Boxed Warning; Indications and Usage; Contraindications; Warnings, including Hepatotoxicity and Adrenal Insufficiency; Dosage and Administration.
   Label revised 2026-08 · Accessed 2026-08-30
   Used for: indication restrictions, hepatotoxicity in patients without risk factors, QT contraindications, adrenal suppression at 400 mg and above, dosing and duration, poor CSF penetration
   DailyMed SPL 1d598696-c6f3-4b7c-ad73-949d2089df35
2. Drugs@FDA via openFDA — applications recorded under the brand name NIZORAL: NDA 018533 tablet 200 mg approved 1981-06-12, NDA 019084 cream 2% approved 1985, NDA 019927 shampoo 2% approved 1990-08-31 and ANDA 070767 oral suspension, all Discontinued with a Federal Register determination that they were not withdrawn for safety or effectiveness reasons; NDA 020310 Nizoral Anti-Dandruff shampoo 1%, approved 1997-10-10, Over-the-counter.
   Accessed 2026-08-30
   Used for: approval dates, which brand forms remain marketed, the basis on which the others were discontinued
   Drugs@FDA, products.brand_name NIZORAL
3. FDA National Drug Code Directory via openFDA, query on ketoconazole.
   Accessed 2026-08-30
   Used for: which presentations are currently listed and their marketing categories, including prescription and over-the-counter topical products
   openFDA NDC Directory
4. FDA Adverse Event Reporting System via openFDA, query on ketoconazole.
   Data cut 2026-07-30 · Accessed 2026-08-30
   Used for: report counts, serious-coded share, most frequently coded reaction terms
   openFDA FAERS

This page is medical information, not medical advice. It covers both a restricted prescription tablet and widely available topical products, and does not replace assessment by a clinician who knows your history, your liver function and your other medicines.