Terbinafine
Terbinafine Hydrochloride
Also known as: Lamisil · Terbinex · Alamil · Daskil · Daskyl · DesenexMax · Finex · Maditez · Micosil · Terekol · Osurnia · Terbinafine hydrochloride · Terbinafinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Dermatophytic infections | 10-20 mg/kg | PO | q24h | — | 🌎 NA |
| Dermatophytic infections (when other drugs are not tolerated) | 25 mg/kg | PO | q24h | — | 🌎 NA |
| Adjunctive treatment of nasal Aspergillus infections (if cribriform plate is penetrated) | 5-10 mg/kg | PO | q12h | 3-6 months | 🌎 NA |
| Pythiosis (where advanced disease precludes complete surgical excision) | 10 mg/kg | PO | q24h | — | 🌎 NA |
| Lagendiosis (where disease precludes complete surgical excision) | 5-10 mg/kg | PO | q24h | — | 🌎 NA |
| Antifungal (Systemic/Dermatophytosis) | 20-40 mg/kg | PO | q24h | Not specified | 🌍 EU |
| Localized Malassezia infections | Apply a thin layer | topical | Not specified | Not specified | 🌍 EU |
| Acute otitis externa (S. pseudintermedius, M. pachydermatis) | 1 tube per infected ear | topical | Repeat after 7 days | 2 doses total | 🌍 EU |
- Dermatophytic infections: Appears to be better tolerated than either ketoconazole or itraconazole.
- Adjunctive treatment of nasal Aspergillus infections (if cribriform plate is penetrated): Used with topical therapy.
- Pythiosis (where advanced disease precludes complete surgical excision): Given concurrently with itraconazole (10 mg/kg PO twice daily).
- Lagendiosis (where disease precludes complete surgical excision): Given concurrently with itraconazole (10 mg/kg PO q24h) and repeated aggressive surgical resection.
- Antifungal (Systemic/Dermatophytosis): Doses greater than 30 mg/kg may be required to reach therapeutic levels in the skin of dogs.
- Localized Malassezia infections: Use 1% cream.
- Acute otitis externa (S. pseudintermedius, M. pachydermatis): Ear gel should be instilled in a cleaned ear. Maximum clinical response may not be seen until 21 days after the second administration.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Dermatophytic infections (Pulse therapy) | 20 mg/kg | PO | q24h | 7 days on, then 21 days off | 🌎 NA |
| Dermatophytic infections | 10-20 mg/kg | PO | q24h | — | 🌎 NA |
| Dermatophytic infections (when other drugs are not tolerated) | 25 mg/kg | PO | q24h | — | 🌎 NA |
| Dermatophyte (M. canis) mycetomas | 26-31 mg/kg | PO | q24h | 12-14 weeks | 🌎 NA |
| Cryptococcal infections (azole-resistant) | 10 mg/kg | PO | q24h | Life-long | 🌎 NA |
| Antifungal (Systemic/Dermatophytosis) | 20-40 mg/kg | PO | q24h | Not specified | 🌍 EU |
| Localized Malassezia infections | Apply a thin layer | topical | Not specified | Not specified | 🌍 EU |
- Dermatophytic infections (Pulse therapy): Maintained terbinafine concentrations in hair above therapeutic levels. Higher doses (40 mg/kg) or continuous administration caused emesis and elevated hepatic enzymes.
- Dermatophytic infections: Appears to be better tolerated than either ketoconazole or itraconazole.
- Dermatophyte (M. canis) mycetomas: Achieved clinical and mycological cure in a case report of two cats.
- Cryptococcal infections (azole-resistant): Can rectify clinical signs, though cats with CNS cryptococcus usually require treatment for life.
- Localized Malassezia infections: Use 1% cream.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Avian mycotic infections (Aspergillus) | 10-15 mg/kg | PO | q12-24h | — | 🌎 NA |
| Avian mycotic infections (Aspergillus) | 1 mg/mL aqueous solution | Nebulization | Not specified | — | 🌎 NA |
| Avian mycotic infections | 10-15 mg/kg | PO | q12-24h | — | 🌎 NA |
| Avian mycotic infections | 1 mg/mL | Nebulization | Not specified | — | 🌎 NA |
| Aspergillosis (suspected via leukocytosis and pulmonary nodules) | 10-15 mg/kg | PO | q12h | 4 weeks | 🌎 NA |
- Avian mycotic infections (Aspergillus): Appears to be well tolerated by a number of avian species.
- Avian mycotic infections: Suspend a 250 mg tablet in 25 mL water. Can be used in combination with itraconazole.
- Avian mycotic infections: Mix 500 mg terbinafine plus 1 mL Mucomyst plus 500 mL of distilled water.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Terbinafine is a synthetic allylamine antifungal agent available in both oral and topical formulations.
Key Clinical Features:
- Primary Use: Highly effective against dermatophytic infections (e.g., Microsporum, Trichophyton) in dogs and cats. It is also utilized for systemic mycotic infections like Aspergillus, particularly in avian species.
- Favorable Interaction Profile: Unlike azole antifungals (e.g., ketoconazole, itraconazole), terbinafine does not rely on the cytochrome P-450 enzyme system for its primary mechanism, resulting in significantly fewer drug interactions and no suppression of mammalian testosterone or cortisol synthesis.
- Pharmacologic Pearl: Terbinafine is highly lipophilic and keratinophilic. It distributes extensively into the skin, sebum, and hair follicles, persisting in these tissues at therapeutic concentrations for weeks even after therapy is discontinued (allowing for pulse-therapy protocols).
- Tolerability: Generally very well tolerated in veterinary patients, with mild gastrointestinal upset (vomiting) being the most commonly reported adverse effect.
Mechanism of action
Terbinafine exerts its antifungal activity by interfering with fungal sterol biosynthesis at an early stage.
- It selectively and reversibly inhibits the fungal enzyme squalene monooxygenase (also known as squalene 2,3-epoxidase).
- This blockade prevents the conversion of squalene to lanosterol → leading to a profound deficiency of ergosterol (a critical component of the fungal cell membrane).
- Simultaneously, the inhibition causes an intracellular accumulation of squalene, which is directly toxic to the fungal cell, leading to rapid cell death.
This dual mechanism makes terbinafine primarily fungicidal against dermatophytes, though it may only be fungistatic against certain yeasts like Candida spp.
Safety & warnings
Contraindications
- Known hypersensitivity to terbinafine
- Active or chronic liver disease
- Significantly impaired renal function
- Perforated eardrum (for ear gel administration)
- Generalized demodicosis (topical or systemic use)
- Pregnant animals
- Breeding animals
Adverse effects
- Vomiting
- Inappetence
- Diarrhea
- Lethargy (reported in cats)
- Hepatotoxicity / Liver failure (very rare, reported in humans)
- Neutropenia (very rare, reported in humans)
- Serious skin reactions like Toxic Epidermal Necrolysis or Stevens-Johnson syndrome (very rare, reported in humans)
- Diarrhoea
- Increased liver enzymes
- Pruritus (cats)
- Topical irritation (due to alcohol content in topical solutions)
- Transient deafness or impaired hearing (in elderly dogs after administration of ear gel)
Precautions
Hepatic and Renal Warning: Use with extreme caution, if at all, in patients with markedly impaired liver or renal function. Dosage adjustments should be considered if use is unavoidable.
- Pregnancy/Nursing: Definitive safety in pregnancy has not been established (FDA Category B in humans). The manufacturer recommends against use in pregnant or nursing individuals, as the drug concentrates in maternal milk at levels 7 times higher than plasma. Use with caution in nursing veterinary patients.
Drug interactions
Terbinafine may increase the elimination and decrease the efficacy of cyclosporine.
May increase terbinafine clearance, potentially requiring higher terbinafine doses.
Terbinafine shares the CYP2D6 metabolic pathway and could theoretically alter the metabolism of beta-blockers.
Terbinafine shares the CYP2D6 metabolic pathway and could theoretically alter the metabolism of MAOIs.
Terbinafine shares the CYP2D6 metabolic pathway and could theoretically alter the metabolism of SSRIs.
Terbinafine shares the CYP2D6 metabolic pathway and could theoretically alter the metabolism of TCAs.
May decrease the clearance of terbinafine, potentially increasing plasma concentrations (Clinical Pearl)
Monitoring
- Clinical efficacy (resolution of fungal lesions)
- Baseline liver enzymes prior to therapy
- Periodic liver enzyme monitoring as needed, especially during long-term treatment
- CBC (baseline and periodic)
- Liver function tests (ALT, AST, Bilirubin)
- Renal function tests
- Clinical response (skin scrapings, fungal cultures)
Pharmacokinetics
Half-life
Absorption
In humans, oral absorption is >70%, but first-pass metabolism reduces bioavailability to about 40%. Food may slightly enhance absorption.
Distribution
Highly lipophilic and keratinophilic. Distributes extensively into the skin, sebum, and adipose tissue, where it can persist for very long periods. >99% bound to plasma proteins.
Metabolism
Metabolized in the liver.
Elimination
Eliminated primarily after hepatic metabolism.
Overdose
There is limited information regarding acute toxicity in veterinary species. In humans, acute ingestions of up to 5 grams have been reported without serious adverse effects. Treatment of massive overdose should be supportive and symptomatic.
Available products
Formulations
- Oral granules
- Aqueous solution (for nebulization)
- 250 mg oral tablets
- 1% topical cream
- 1% topical gel
- 1% topical spray
- 10 mg ear gel (combination product containing terbinafine, florfenicol, and betamethasone)
Veterinary
- Osurnia ear gel (10 mg terbinafine, florfenicol, betamethasone)
Human-labeled
- Terbinafine HCl Oral Tablets: 250 mg (Lamisil, Terbinex, generic)
- Terbinafine HCl Oral Granules (film-coated): 125 mg/packet & 187.5 mg/packet (Lamisil)
- Topical cream 1%
- Topical spray 1%
- Lamisil 250 mg tablets
- Lamisil 1% cream
- Lamisil 1% gel
- Lamisil 1% spray
Regulatory status
POM-V
POM-V, POM
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store tablets at room temperature in tight containers; protect from light.
Client information
Important Information for Pet Owners
- Administration: It is highly recommended to give this medication with food. This helps increase absorption and significantly reduces the chance of stomach upset or vomiting.
- Treatment Duration: Fungal infections (like ringworm) take time to heal. You may need to give this medication for several weeks or months. Do not stop early, even if your pet looks better, unless instructed by your veterinarian.
- What to Watch For: Terbinafine is generally very safe. However, contact your veterinarian if your pet experiences persistent vomiting, loss of appetite, severe diarrhea, or extreme tiredness.
- Rare but Serious Signs: In very rare cases, this drug can affect the liver. Call your vet immediately if you notice a yellowing of the eyes, gums, or skin (jaundice).
- Cost: Be aware that a full course of treatment can be relatively expensive, though generic options have made it more affordable.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.