Itraconazole

Itraconazole is a triazole antifungal used for dermatophyte, yeast and selected systemic fungal infections. Its affinity for skin and keratinized tissues supports treatment of dermatophytosis and Malassezia-associated disease. In veterinary systemic mycoses, important applications include blastomycosis, histoplasmosis and selected cryptococcal or coccidioidal infections. Oral formulations differ in bioavailability.

Group

Triazole antifungal

Mechanism of Action

Itraconazole inhibits fungal lanosterol 14-alpha-demethylase, reducing synthesis of ergosterol needed for normal cell-membrane structure. Depletion of ergosterol and accumulation of abnormal sterols impair membrane function and suppress fungal growth. Its activity is usually fungistatic against susceptible fungi. Distribution into skin, sebum and keratinized tissues supports sustained antifungal exposure at cutaneous infection sites.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Systemic fungal infection — Loading	20 mg/kg	PO
Systemic fungal infection — Maintenance	10 mg/kg	PO	Every 24 h
Systemic fungal infection — Maintenance	5 mg/kg	PO	Every 12 h	Divided-dose alternative.
Highly susceptible fungal infection	5 mg/kg	PO	Every 24 h
Dermatophytosis	3 mg/kg	PO	Every 24 h	Up to 15 days
Cryptococcosis	5 mg/kg	PO	Every 12 h
Malassezia dermatitis	Reference only	PO		5 mg/kg every 24 hours for 2 days each week, repeated for 3 weeks. This pulse schedule requires the specified on/off calendar.
Malassezia dermatitis	5 mg/kg	PO	Every 24 h	Up to 21 days
Dermatophytosis	5 mg/kg	PO	Every 24 h	Culture follow-up after 4 weeks; continue at least 2 weeks beyond clinical cure and until serial cultures are negative.
Dermatophytosis pulse treatment	Reference only	PO		5 mg/kg daily for 7 days, then 7 days off, for three treatment pulses; do not replace with an uninterrupted course.
Blastomycosis	5 mg/kg	PO	Every 24 h	Usually at least 60-90 days and at least 30 days beyond complete clinical resolution.
Blastomycosis — Loading	10 mg/kg	PO	Every 24 h	Up to 3 days; Separate three-day loading alternative; then total 5 mg/kg/day, either daily or divided twice daily.
Blastomycosis — Maintenance	2.5 mg/kg	PO	Every 12 h	Exact divided alternative to the total 5 mg/kg/day schedule.
Histoplasmosis	10 mg/kg	PO	Every 24 h	Usually months of treatment and at least 30 days beyond clinical resolution. Severe intestinal disease may require amphotericin B before oral itraconazole.
Coccidioidomycosis	5–10 mg/kg	PO	Every 24 h	Courses may extend 6-12 months.
Sporotrichosis	5–10 mg/kg	PO	Every 24 h	Continue for 30 days beyond complete lesion resolution.
Coccidioidomycosis	5 mg/kg	PO	Every 12 h
Nasal aspergillosis or chronic lymphoplasmacytic rhinitis	5 mg/kg	PO	Every 12 h	Clinical use usually 3-6 months; nasal-aspergillosis efficacy is inconsistent.
Pythiosis or lagenidiosis combined therapy	Reference only	PO		After resection, itraconazole 10 mg/kg daily plus terbinafine 5-10 mg/kg daily for at least 2 months; not a single-drug protocol.
Zygomycosis	5–10 mg/kg	PO	Every 24 h	After aggressive resection; nonresectable disease may require 3-6 months and relapse is possible.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Systemic fungal infection	5 mg/kg	PO	Every 24 h
Systemic fungal infection	50 mg/animal	PO	Every 24 h	Separate fixed-dose alternative; choose a patient-appropriate regimen.
Systemic fungal infection	100 mg/animal	PO	Every 48 h	Separate alternate-day fixed-dose alternative.
Dermatophytosis	Reference only	PO		5 mg/kg daily during weeks 1, 3 and 5, with weeks 2 and 4 off treatment; three treatment cycles. Further treatment depends on clearance.
Histoplasmosis	10 mg/kg	PO	Every 24 h	Usually months of treatment and at least 30 days beyond clinical resolution. Severe intestinal disease may require amphotericin B before oral itraconazole.
Histoplasmosis	5 mg/kg	PO	Every 12 h	Divided alternative to 10 mg/kg/day.
Blastomycosis	10 mg/kg	PO	Every 24 h	Usually 2-3 months or longer; cats may require longer courses than dogs.
Blastomycosis	5 mg/kg	PO	Every 12 h	Divided alternative.
Coccidioidomycosis	5–10 mg/kg	PO	Every 24 h	Courses may extend 6-12 months.
Sporotrichosis	5–10 mg/kg	PO	Every 24 h	Continue for 30 days beyond complete lesion resolution.
Cryptococcosis	50–100 mg/animal	PO	Every 24 h	Long courses, with antigen-titre and liver monitoring; choose dose according to patient size and disease site.
Coccidioidomycosis	25–50 mg/animal	PO	Every 12–24 h	Fixed-dose alternative; long-course treatment requires reassessment.
Dermatophytosis	5 mg/kg	PO	Every 12 h	Separate continuous regimen; culture-guided duration, commonly 3-5 weeks.
Dermatophyte granuloma	10 mg/kg	PO	Every 24 h	Continue at least a month beyond clinical resolution and until two brush cultures are negative.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Systemic fungal infection	5 mg/kg	PO	Every 24 h	Use commercial oral solution; capsules are poorly absorbed.
Systemic fungal infection	2.5 mg/kg	PO	Every 12 h	Divided-dose alternative using oral solution.
Guttural pouch mycosis or fungal rhinitis or osteomyelitis	5 mg/kg	PO	Every 24 h	Commercial oral solution; capsule absorption is poor.
Fungal keratitis topical treatment	Reference only	TOPICAL		Compounded 1% itraconazole in 30% DMSO, with the suspension vehicle completed using artificial tears, applied to the cornea initially every 2-3 hours then tapered to response. DMSO may irritate and enhances skin uptake; wear gloves.

Birds

Use / stage	Dose	Route	Schedule	Instructions
Ratite fungal infection	6–10 mg/kg	PO	Every 24 h	Reduce or stop for neurologic signs.
Fungal infection	5–10 mg/kg	PO	Every 12–24 h	African grey parrots are unusually sensitive; use the lower species-specific alternative or another antifungal.
Amazon-parrot aspergillosis	5–10 mg/kg	PO	Every 24 h	Amazon parrots only.
African-grey-parrot aspergillosis	2.5–5 mg/kg	PO	Every 24 h	African grey parrots only; monitor anorexia and depression closely.

Indications

Treatment of dermatophytosis in cats and dogs, including Microsporum canis infection.
Treatment of Malassezia dermatitis and selected other susceptible superficial yeast infections.
Treatment of blastomycosis and histoplasmosis in dogs, cats and selected other veterinary species.
Treatment of selected cryptococcosis or coccidioidomycosis cases with an organism- and site-appropriate regimen.
Treatment of selected sporotrichosis, including feline or equine disease.
Treatment of selected other susceptible systemic fungal infections in exotic or zoo patients.

Contraindications

Use cautiously with hepatic disease or pregnancy.
Avoid unvalidated compounded products with unreliable absorption.
Reduced cardiac function: itraconazole may exert negative inotropic effects. African grey parrots have increased susceptibility to anorexia and depression.

Interactions

Acid suppressants reduce capsule absorption.
CYP inhibition can increase cyclosporine and other narrow-margin drug concentrations.

Adverse effects

Vomiting, anorexia and increased liver enzymes
Hepatotoxicity and canine vasculitic or ulcerative skin lesions

Toxicity

Stop treatment for hepatic injury or severe cutaneous reactions and provide appropriate support.

Preparations

Preparation	Form	Strength	Route
Itraconazole 100 mg capsule	Capsule	100 mg / capsule	PO
Itrafungol 10 mg/mL oral solution Cyclodextrin solution for cats.	Oral Liquid	10 mg / mL	PO
Sporanox 10 mg/mL oral solution Commercial cyclodextrin solution.	Oral Liquid	10 mg / mL	PO

Monitoring and Administration

Give capsules with food; cyclodextrin oral solution has different administration requirements and better absorption, especially in cats and horses.

Monitor liver enzymes; trough concentrations of 0.5-1 mcg/mL are a reported target when drug monitoring is used.

Do not freeze commercial oral solution. For the described IV presentation, use saline rather than dextrose or lactated Ringer’s; infuse over 30 minutes and do not mix with other drugs. The described diluted solution was stable for up to 48 hours.

Compounded suspensions and capsules may have very poor absorption; do not assume bioequivalence.

Malassezia pulse therapy and feline dermatophyte alternate-week therapy are kept readable because the app cannot encode on/off treatment calendars.

Experimental rodent regimens list mice 50-150 mg/kg/day for blastomycosis, rats 2.5-10 mg/kg/day for vaginal candidiasis and guinea pigs 5 mg/kg/day for systemic candidiasis, but administration routes are not supplied; they are not generalized into route-specific prescriptions.