Terbinafine: veterinary dose and monograph

At a glance

Drug class

Antifungal

Also known as

Lamisil

Species with doses

Dogs, Cats, Horses, Birds and Hedgehogs

General dose range

30–40 mg/kg PO q24h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Dermatophytosis (Microsporum, Trichophyton) — dogs and cats
• Malassezia dermatitis (adjunct)
• Refractory fungal nail / claw infections
• Aspergillosis (adjunctive, avian / raptor)

Terbinafine 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

• Dermatophytosis: Papich 5e: 30–40 mg/kg q24h PO with food for 2–3 weeks. Plumb’s p.1101 lists lower doses — 10–20 mg/kg once daily (MacDonald 2008) or 25 mg/kg q24h when other drugs are not tolerated (Rosenkrantz 2006). Continue until 2 negative cultures.
• Nasal aspergillosis (adjunct, cribriform plate breached): Plumb’s p.1101 (Kuehn 2007): 5–10 mg/kg PO q12h for 3–6 months with topical therapy. Pythiosis: 10 mg/kg q24h with itraconazole 10 mg/kg q12h (Marks 2007).

Cats

• Dermatophytosis: Papich 5e: 30–40 mg/kg/day PO for at least 2 weeks (or ¼ tablet = 62.5 mg for small cats, ½ tablet for medium, 1 tablet for large cats, once daily). Plumb’s p.1101 (Balda & Larsson 2009): pulse therapy 20 mg/kg once daily for 7 days then 21 days off cured cats; 40 mg/kg or continuous dosing caused emesis and raised liver enzymes in some cats.

Horses

• Fungal infection (efficacy unproven): Papich 5e: horses 30 mg/kg PO q12h — no studies demonstrate efficacy in horses.

Birds

• Aspergillosis (adjunct): Plumb’s p.1101: 10–15 mg/kg PO q12–24h, well tolerated in many species (Black 2008; Flammer 2003); suspected aspergillosis 10–15 mg/kg PO q12h for 4 weeks (Lichtenberger & Orosz 2007). Nebulisation 1 mg/mL. Can be combined with itraconazole.

Hedgehogs

• Dermatophytosis: Carpenter Exotic Animal Formulary 6th ed, Table 8-2 (p.514): European hedgehogs 100 mg/kg PO q12h in food — 93% culture-negative by 14 days, 99% by 28 days (safety not formally assessed). Considered a safe, effective dermatophytosis option.

Contraindications

Significant hepatic impairment. Use cautiously with other hepatotoxic drugs.

Adverse effects

• Occasional GI upset / vomiting
• Facial pruritus or hypersalivation (cats)
• Mild, usually reversible hepatic enzyme elevation

Drug interactions

• Cyclosporine: terbinafine may INCREASE the elimination of cyclosporine (the opposite direction to ketoconazole, which raises it) — do not assume the azole interaction applies
• Rifampin: may increase terbinafine clearance
• Shares the CYP2D6 pathway, so terbinafine could affect the metabolism of beta-blockers
• MAO inhibitors (amitraz, selegiline): CYP2D6 pathway interaction
• SSRIs (fluoxetine and others): CYP2D6 pathway interaction
• Tricyclic antidepressants: CYP2D6 pathway interaction

Toxicity and overdose

Plumb's p.1101: limited information — humans have taken doses of up to 5 grams without serious effects, so the acute margin appears wide. Terbinafine is generally very well tolerated in dogs and cats, with vomiting the most likely adverse effect; experience remains limited. Use caution in liver or renal disease and monitor liver enzymes on prolonged courses.

Clinical pearls

• The one azole problem terbinafine does NOT have: no cytochrome P450 involvement, so no P450 drug interactions and no suppression of cortisol or testosterone
• Persists in keratin for weeks — pulse protocols (2 wk on / 1 wk off) work well and cut cost
• Combine with topical antifungal therapy and environmental decontamination for true M. canis cure
• Better tolerated than ketoconazole / itraconazole — a good choice when azoles cause anorexia

Mechanism of action

Plumb's pp.1100–1101: ALLYLAMINE antifungal. Inhibits squalene monooxygenase (squalene 2,3-epoxidase), blocking conversion of squalene to sterols — especially ergosterol — so the fungal membrane is both depleted of ergosterol and loaded with accumulated squalene; both effects contribute to killing. This mechanism is DIFFERENT from the azoles, which act further down the same pathway. Clinically decisive consequence: terbinafine is not mediated by cytochrome P450, so unlike ketoconazole and itraconazole it carries none of the P450 interaction burden and does NOT alter testosterone or cortisol. FUNGICIDAL against dermatophytes (Microsporum, Trichophyton); only fungistatic against yeasts (Candida). It has activity against Aspergillus, Blastomyces and Histoplasma but is not usually used clinically for those.

Formulations and products

• Terbinafine 250 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

• Lime Sulfur (Lime Sulphur Dip)
• Miconazole
• Nystatin
• Posaconazole
• Voriconazole

Frequently asked questions