Fluconazole

Fluconazole is a triazole antifungal used for selected yeast and systemic fungal infections in veterinary patients. Its water solubility, penetration into cerebrospinal fluid and active urinary excretion support use at central nervous system and urinary sites. Important applications include cryptococcosis and coccidioidomycosis, with activity depending on the fungal species and susceptibility.

Group

Triazole antifungal

Mechanism of Action

Fluconazole inhibits fungal lanosterol 14-alpha-demethylase, a cytochrome P450 enzyme required for ergosterol synthesis. Reduced ergosterol and accumulation of abnormal sterols disrupt membrane structure and function, suppressing fungal growth. The effect is primarily fungistatic against susceptible fungi. Distribution into cerebrospinal fluid and urine supports treatment of susceptible organisms at those sites.

Dose Rates

Dog

Use / stage	Dose	Route	Schedule	Instructions
Fungal infection	5 mg/kg	PO, IV	Every 12 h
Refractory fungal infection	10 mg/kg	PO, IV	Every 12 h
Malassezia dermatitis	5 mg/kg	PO	Every 12 h
Blastomycosis	5 mg/kg	PO	Every 12 h	Up to 60 days

Cat

Use / stage	Dose	Route	Schedule	Instructions
Fungal infection	50 mg/animal	PO	Every 24 h
Refractory fungal infection	50 mg/animal	PO	Every 12 h
Refractory fungal infection	10 mg/kg	PO	Every 12 h	Weight-based alternative to fixed 50 mg doses.

Horse

Use / stage	Dose	Route	Schedule	Instructions
Fungal infection	5 mg/kg	PO	Every 24 h

Rabbit

Use / stage	Dose	Route	Schedule	Instructions
Systemic fungal infection	25–43 mg/kg	IV	Every 12 h	Slow administration.

Bird

Use / stage	Dose	Route	Schedule	Instructions
Candidiasis	20 mg/kg	PO	Every 24–48 h	PK-based proposal in Goffin cockatoos, Timneh African greys and orange-winged Amazons; less-susceptible Candida species may not respond.
Candidiasis	10 mg/kg	PO	Every 24 h	PK-based alternative for susceptible C. albicans.
Aspergillosis adjunct	5–10 mg/kg	PO	Every 24 h	Up to 42 days; Alternative with or after amphotericin B.

Indications

Treatment of cryptococcosis in cats, dogs and selected other veterinary species, including some nasal, ocular or central nervous system infections.
Treatment of coccidioidomycosis in dogs and selected other patients.
Treatment of susceptible Candida or other fungal urinary tract infections.
Treatment of selected other susceptible systemic mycoses within a disease-specific antifungal plan.
Treatment of selected susceptible Malassezia dermatitis or other cutaneous yeast infections in dogs.

Contraindications

Use cautiously in pregnancy.

Interactions

May raise cyclosporine and other CYP-metabolized drug concentrations; anesthetic recovery may be prolonged.

Adverse effects

Hepatic enzyme elevations and hepatopathy

Preparations

Preparation	Form	Strength	Route
Fluconazole 50 mg	Tablet	50 mg / tablet	PO
Fluconazole 100 mg	Tablet	100 mg / tablet	PO
Fluconazole 150 mg	Tablet	150 mg / tablet	PO
Fluconazole 200 mg	Tablet	200 mg / tablet	PO
Fluconazole oral suspension 10 mg/mL	Oral Liquid	10 mg / mL	PO
Fluconazole oral suspension 40 mg/mL	Oral Liquid	40 mg / mL	PO
Fluconazole IV solution 2 mg/mL	Injection	2 mg / mL	IV

Monitoring and Administration

Monitor liver enzymes and clinical response. Activity against Aspergillus and other molds is poor.

Oral absorption is relatively reliable without food. Reconstituted commercial suspension generally has a 14-day use period; compounded concentration accuracy can vary.

Canine blastomycosis dose is listed as 10 mg/kg/day without an explicit route in that entry; retained here rather than assigning an unconfirmed route.

The avian drinking-water concentration is printed as 100 mg/mL in the additional text and is inconsistent with ordinary drinking-water dosing; it is not a usable mixing instruction.