Ketoconazole for Dogs Dosage Calculator
Veterinary ketoconazole dosing for dogs — covering systemic fungal infections, Malassezia dermatitis, and off-label Cushing’s disease management with tablet breakdown and hepatotoxicity monitoring guidance.
Hepatotoxicity risk — monitor liver enzymes. Ketoconazole inhibits hepatic CYP450 enzymes and can cause hepatotoxicity. Obtain baseline ALT/ALP before treatment; recheck every 2–4 weeks during therapy. Give with food to improve bioavailability and reduce GI upset.
About Ketoconazole (Nizoral / Ketoseb)
Drug Class
Imidazole Antifungal and Cortisol Synthesis Inhibitor
Mechanism of Action
Ketoconazole inhibits cytochrome P450-dependent lanosterol 14α-demethylase, blocking ergosterol synthesis in fungal cell membranes. In high doses, it also inhibits mammalian CYP3A4, CYP17, and CYP11B1, suppressing cortisol and sex steroid synthesis. It is a potent CYP3A4 inhibitor — major drug interaction risk.
Primary Uses in Dogs
Superficial and systemic fungal infections (Malassezia, Candida, dermatophytes, Aspergillus, Blastomyces, Coccidioides, Histoplasma). Off-label: medical management of hyperadrenocorticism (Cushing’s disease) when trilostane is unavailable.
Dosing Quick Reference
| Indication | Dose | Frequency |
|---|---|---|
| Dermatophytosis / Malassezia | 2.5–5 mg/kg | q12h PO with food |
| Systemic fungal infection | 5–10 mg/kg | q12h PO with food |
| Cushing’s disease (off-label) | 5–15 mg/kg | q12h PO |
Common Side Effects
- Anorexia and nausea (most common — give with food)
- Vomiting and diarrhoea
- Elevated liver enzymes (ALT/ALP) — dose-dependent hepatotoxicity
- Adrenal suppression (inhibits cortisol synthesis)
- Coat lightening or alopecia (rare)
- Thrombocytopenia (rare)
Monitoring
ALT and ALP every 2 weeks during treatment. Bile acids or ACTH stimulation test if adrenal suppression is suspected. Discontinue if ALT rises > 3× upper limit of normal.
What Is Ketoconazole for Dogs?
Ketoconazole is an imidazole antifungal that inhibits fungal lanosterol 14α-demethylase (CYP51), blocking ergosterol synthesis and disrupting fungal cell membrane integrity. In dogs it is used for systemic mycoses (blastomycosis, histoplasmosis, coccidioidomycosis, cryptococcosis), Malassezia dermatitis and otitis, and off-label for hyperadrenocorticism (Cushing’s disease) by inhibiting adrenal steroidogenesis.
Ketoconazole requires gastric acid for dissolution and absorption — give with food. Bioavailability varies significantly; patients on antacids or PPIs may have reduced absorption. It is available as 200 mg tablets.
Indications and Dose Ranges
- Systemic fungal infections: 5–10 mg/kg PO q12–24h (duration by infection type)
- Malassezia dermatitis: 5–10 mg/kg PO q24h × 3–4 weeks
- Cushing’s disease (off-label): 15 mg/kg PO q12h — titrate to effect, monitor cortisol
- Steroidogenesis inhibition (adjunct): 5–15 mg/kg q12h
How to Use This Calculator
- Enter your dog’s weight in kg or lbs
- Select the indication to apply the correct dose range
- Click Calculate to see dose per administration and tablet count
- Always give with food; obtain baseline liver panel
🧮 Ketoconazole Dose Calculator
Ketoconazole Dosing Result
Drug Interactions
- Cyclosporine: Ketoconazole significantly increases cyclosporine levels — major interaction, dose reduction needed
- Antacids / PPIs / H2 blockers: Reduce ketoconazole absorption — separate by 2 hours
- Phenobarbital / rifampicin: Reduce ketoconazole plasma levels
- Warfarin / anticoagulants: Increased anticoagulant effect — monitor clotting times
- Cisapride / certain antiarrhythmics: QT prolongation risk — avoid combination
References
- Plumb DC. Plumb’s Veterinary Drug Handbook, 9th ed. Wiley-Blackwell; 2018.
- Papich MG. Saunders Handbook of Veterinary Drugs, 4th ed. Elsevier; 2016.
- Bruyette DS. Hyperadrenocorticism in dogs. In: Ettinger SJ, ed. Textbook of Veterinary Internal Medicine. 7th ed. Saunders; 2010.
- Moriello KA. Dermatophytosis in dogs. Vet Clin North Am Small Anim Pract. 2004;34(2):411-429.