Ketoconazole: veterinary dose and monograph

At a glance

Drug class

Antifungal

Also known as

Nizoral, Keto

Species with doses

Dogs, Cats and Hedgehogs

General dose range

5–10 mg/kg PO q12h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Malassezia dermatitis / otitis (canine)
• Systemic mycoses where itraconazole is unavailable
• Cyclosporine dose-sparing (CYP3A inhibition)
• Adjunct medical management of hyperadrenocorticism

Ketoconazole dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Malassezia dermatitis: Papich 5e: Malassezia 5 mg/kg q24h PO. Plumb’s p.699: 5 mg/kg once daily up to 10 mg/kg twice daily (Merchant 2009); 5–10 mg/kg daily for 10 days then every other day for 10 days (Muse 2000). Give with food. Hepatotoxic; inhibits cortisol synthesis and CYP3A (raises cyclosporine levels).
• Systemic mycosis: Papich 5e: 10–15 mg/kg q8–12h PO. Plumb’s p.699: blastomycosis 10 mg/kg PO twice daily for at least 3 months (15–20 mg/kg twice daily with CNS involvement), often with amphotericin B; coccidioidomycosis 5–10 mg/kg twice daily for 3–6 months or longer. Itraconazole is usually more effective.
• Hyperadrenocorticism (when mitotane/trilostane unsuitable): Papich 5e: start 5 mg/kg q12h, increase after 7 days to 12–15 mg/kg q12h. Plumb’s p.699: 5 mg/kg q12h for 5–7 days, then 10 mg/kg q12h for 10–14 days and ACTH stimulation test; up to 15 mg/kg q12h. Over 25% of dogs do not respond.

Cats

• Systemic mycoses: Papich 5e: cats 5–10 mg/kg q8–12h PO. Monitor appetite and liver enzymes — anorexia and hepatotoxicity are common; itraconazole or fluconazole are usually preferred in cats.

Hedgehogs

• Dermatophytosis / Candida: Carpenter Exotic Animal Formulary 6th ed, Table 8-2 (p.514): hedgehogs 10 mg/kg PO q24h for 6–8 weeks. Long-course dermatophytosis / Candida therapy.

Contraindications

Cats (poorly tolerated — anorexia, hepatotoxicity; use itraconazole instead). Hepatic disease. Pregnancy (teratogen, inhibits steroidogenesis). Many CYP interactions.

Species-specific warnings

Cats: Avoid in cats — frequent anorexia and hepatotoxicity; itraconazole or fluconazole are safer feline choices.

Adverse effects

• Anorexia, vomiting (common)
• Hepatotoxicity (idiosyncratic and dose-related)
• Reversible suppression of cortisol and testosterone synthesis
• Lightening of the hair coat (chronic use)

Drug interactions

• Alcohol: may produce a disulfiram-like reaction (vomiting)
• Antacids: reduce oral absorption — give ketoconazole at least 1 hour before or 2 hours after
• Tricyclic antidepressants (amitriptyline, clomipramine): reduced metabolism, increased adverse effects
• Benzodiazepines (midazolam, triazolam): levels increased
• Buspirone: plasma concentrations may be elevated
• Busulfan: levels may be increased
• Calcium-channel blockers (amlodipine, verapamil): levels may be increased
• Cisapride: raised levels with toxicity risk — contraindicated together in humans
• Cyclosporine: ketoconazole markedly raises cyclosporine levels — this is used deliberately to reduce cyclosporine cost, but requires level monitoring
• Ivermectin: Plumb's advises that in dogs at risk of the ABCB1-1delta (MDR1) mutation, ivermectin should never be combined with ketoconazole unless the dog has tested normal

Pregnancy and lactation

Contraindicated — teratogenic and inhibits sex-steroid synthesis.

Toxicity and overdose

Plumb's p.698: no reports of acute toxicity from overdose were located; the oral LD50 in dogs is >500 mg/kg. Should an acute overdose occur the manufacturer recommends supportive measures including gastric lavage with sodium bicarbonate. The real-world problems are chronic rather than acute: hepatotoxicity (the dose-limiting toxicity — monitor liver enzymes), anorexia and vomiting, and the endocrine consequences of P450 inhibition (suppressed cortisol and testosterone). Cats tolerate ketoconazole notably less well than dogs.

Clinical pearls

• Needs an acidic stomach — never co-administer with antacids, H2 blockers or PPIs
• Its CYP3A inhibition is exploited to lower the dose (and cost) of cyclosporine — monitor cyclosporine levels
• Prefer itraconazole or fluconazole when tolerability or feline use matters

Mechanism of action

Plumb's p.697: IMIDAZOLE antifungal. At usual doses and serum concentrations ketoconazole is FUNGISTATIC; at higher concentrations, over prolonged periods, or against very susceptible organisms it can be fungicidal. It increases fungal cell-membrane permeability with secondary metabolic effects and growth inhibition — the exact mechanism is not fully determined but is attributed to interference with ergosterol synthesis, with the fungicidal action possibly a direct membrane effect. Active against most pathogenic fungi including Blastomyces, Coccidioides, Cryptococcus, Histoplasma, Candida and dermatophytes. Clinically important secondary property: it also inhibits mammalian cytochrome P450 steroid synthesis, which is why it both lowers cortisol (exploited in hyperadrenocorticism) and suppresses testosterone.

Formulations and products

• Ketoconazole 200 mg tablet

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other antifungals

• Enilconazole
• Fluconazole
• Griseofulvin
• Itraconazole
• Lime Sulfur (Lime Sulphur Dip)
• Miconazole
• Nystatin
• Posaconazole

Frequently asked questions