Fluconazole: veterinary dose and monograph

At a glance

Drug class

Antifungal

Also known as

Diflucan, Forcan, Zocon, Fluka

Species with doses

Dogs, Cats, Horses, Birds, Rabbits and Primates

General dose range

5–10 mg/kg PO q12–24h — check the species tables for the indication

Routes

PO, IV

Last reviewed

1 October 2026

Indications

• Cryptococcosis (including CNS) — drug of choice for CNS penetration
• Candidiasis (systemic, urinary, mucosal)
• Coccidioidomycosis, some histoplasmosis/blastomycosis (often itraconazole preferred for the latter two)
• Fungal urinary tract infection (renally excreted, active in urine)
• Dermatophytosis and Malassezia (alternative)

Fluconazole 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

• Systemic mycosis / cryptococcosis: Papich 5e: 5 mg/kg q12h PO or IV, up to 10 mg/kg q12h in refractory cases; blastomycosis 10 mg/kg/day. Plumb’s p.530: general 2.5–5 mg/kg q12–24h for 56–84 days (double dose on day 1); fungal meningitis 5–8 mg/kg q12h or 8–12 mg/kg q24h; cryptococcosis 5–15 mg/kg q12–24h for 6–10 months (Lemarie); nasal aspergillosis 2.5–5 mg/kg q12h for 3–6 months. Continue ≥2 months beyond clinical resolution; give IV over 1–2 h.
• Fungal UTI: Plumb’s p.530 (Greene 2006): urinary candidiasis 5–10 mg/kg PO q24h for 21–42 days; Candida glabrata 12 mg/kg PO once daily for 21–42 days. Fluconazole is excreted unchanged in urine.
• Malassezia dermatitis: Plumb’s p.530: 5 mg/kg PO once daily (Thomas; Ihrke — recurrent cases 3 times weekly); 2–5 mg/kg once daily (Beale & Murphy). Papich 5e: 5 mg/kg q12h PO. May be safer than keto- or itraconazole with liver disease.

Cats

• Cryptococcosis (incl. CNS) / candidiasis: Papich 5e: 50 mg per cat once daily, increasing to 50 mg q12h (≈10 mg/kg q12h) in refractory cases. Plumb’s p.530 (Greene 2006): nasal/dermal cryptococcosis 5–10 mg/kg q12–24h (50 mg per cat once daily adequate for most); CNS, ocular or multisystemic 50–100 mg per cat q12h. Treat until antigen negative (usually ≥2 months beyond clinical resolution).

Horses

• Systemic mycosis / Candida: Papich 5e: 5 mg/kg q24h PO. Plumb’s p.530 (Stewart 2008): loading dose 14 mg/kg then 5 mg/kg PO once daily for Coccidioides or Candida bacteraemia.

Birds

• Candidiasis / systemic mycosis: Plumb’s p.530: candidiasis 20 mg/kg PO q24–48h or 10 mg/kg q24h in cockatoos, African greys and Amazons (Flammer 2008); cockatiels 10 mg/kg PO or medicated water (Ratzlaff & Flammer 2009); aspergillosis 5–10 mg/kg PO once daily for up to 6 weeks with or after amphotericin B (Oglesbee).

Rabbits

• Systemic mycosis: Plumb’s p.530 (Ivey & Morrisey 2000): rabbits 25–43 mg/kg slow IV q12h.

Primates

• Cryptococcosis / candidiasis (marmosets, tamarins): Carpenter Exotic Animal Formulary 6th ed, Table 13-2 (p.684): guenon 7 mg/kg PO q24h (Cryptococcus); mandrills/tamarins/marmosets 25 mg/kg/day PO for Candida.

Contraindications

Significant hepatic impairment (reduce dose/monitor). Pregnancy (teratogenic at higher doses). Concurrent drugs with dangerous CYP-mediated interactions (see interactions). Known azole hypersensitivity. Adjust dose in renal impairment (renally excreted).

Species-specific warnings

Cats: A mainstay for feline cryptococcosis (often with nasal/CNS involvement); long courses are typical — monitor liver values and follow antigen titres.

Adverse effects

• GI upset (anorexia, vomiting)
• Hepatotoxicity (less than other azoles, but monitor)
• Skin reactions/rash
• Rare: thrombocytopenia, raised liver enzymes

Drug interactions

• CYP inhibitor: raises levels of cyclosporine, theophylline, midazolam, some benzodiazepines, sulfonylureas, phenytoin
• Warfarin: potentiated anticoagulation
• Other QT-prolonging drugs (e.g. cisapride): increased arrhythmia risk
• Rifampin: induces metabolism, lowering fluconazole levels
• Antacids do NOT meaningfully reduce absorption (unlike ketoconazole/itraconazole)

Pregnancy and lactation

Avoid in pregnancy where possible — azoles are teratogenic at higher/chronic doses. Use only if the systemic mycosis threatens the dam and no safer option exists.

Monitoring

• Liver enzymes (baseline and periodically on long courses)
• Renal function (dose adjustment) — renally excreted
• Clinical/antigen response (e.g. cryptococcal antigen titres) to guide treatment duration
• Review co-medications for CYP interactions

Toxicity and overdose

Generally well tolerated; overdose/chronic use can cause hepatotoxicity and GI upset. Less hepatotoxic and fewer interactions than ketoconazole, but the CYP-inhibition interaction profile and dose-dependent liver effects still require monitoring on long courses.

Management: No specific antidote. Supportive care; decontaminate if a large recent ingestion. Monitor and support liver function. Because it is dialysable and renally cleared, fluid therapy aids elimination; manage hepatotoxicity with hepatoprotectants (SAMe, silybin) and discontinuation.

Clinical pearls

• The azole that reaches the brain, eye and urine — first choice for CNS cryptococcosis and fungal UTI
• Absorption is independent of stomach acid, so antacids/PPIs don't sabotage it (unlike itraconazole/ketoconazole)
• Better tolerated with fewer interactions than ketoconazole — but still check CYP-metabolised co-medications
• Treat systemic mycoses for weeks beyond apparent cure and follow antigen titres (e.g. cryptococcal) where available
• Reduce the dose in renal impairment; watch the liver on long courses

Mechanism of action

Inhibits the fungal cytochrome-P450 enzyme 14-α-demethylase (CYP51), blocking conversion of lanosterol to ergosterol. Ergosterol depletion plus accumulation of toxic methylated sterol precursors damages the fungal cell membrane — a fungistatic effect. Its small, water-soluble structure gives outstanding penetration into CSF, the eye and urine that other azoles lack.

Formulations and products

• 50 mg tablet/capsule
• 100 mg tablet/capsule
• 150 / 200 mg tablet
• IV infusion 2 mg/mL
• Oral suspension 10 mg/mL
• Forcan — 50 / 100 / 150 / 200 mg tablet, Tablet (human-label)
• Zocon — 50 / 150 / 200 mg tablet; suspension, Tablet / suspension (human-label)
• Fluconazole IV — 2 mg/mL (100 mL), IV infusion (human-label)

Storage

Tablets/capsules: 15–30 °C, dry. Oral suspension: per label (often refrigerated, shake well). IV: room temperature, protect from light.

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

• Amphotericin B
• Caspofungin
• Clotrimazole
• Enilconazole
• Griseofulvin
• Itraconazole
• Ketoconazole
• Lime Sulfur (Lime Sulphur Dip)

Frequently asked questions