Fluconazole (Diflucan®) for Dogs and Cats

Overview of Fluconazole for Dogs and Cats

• Fluconazole, also known as Diflucan®, belongs to a general class of drugs known as antifungals. Other related drugs in this class include miconazole, itraconazole (Sporanox®), and ketoconazole (Nizoral®). Fluconazole is used in both dogs and cats to treat infections caused by fungi.
• Fluconazole inhibits the growth of fungal organisms by interfering with the formation of the fungal cell wall.
• It is effective only against fungal or yeast organisms. These fungi are the ones that cause skin infections (dermatophytes) commonly known as “ringworm” and toenail infections. However, it also is effective for some more serious fungal infections, such as blastomycosis and cryptococcosis. These infections can affect the brain, bones, and respiratory tract (lungs).
• Fluconazole is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
• This drug is not approved for use in animals by the Food and Drug Administration, but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names Fluconazole

• This drug is registered for use in humans only.
• Human formulations: Diflucan® (Roerig)
• Veterinary formulations: None

Uses of Fluconazole for Dogs and Cats

• Fluconazole is used in both dogs and cats to treat infections caused by fungi. These infections may affect the skin, claws, brain, respiratory tract, bones, and other tissues.
• It is not effective against infections caused by bacteria, parasites (intestinal worms), mites, or viruses.

Fluconazole for Dogs: Side Effects

• While generally safe and effective when prescribed by a veterinarian, fluconazole can cause side effects in some animals.
• Fluconazole should not be used in animals with known hypersensitivity or allergy to the drug.
• Fluconazole may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with fluconazole. Such drugs include glipizide, cimetidine, amphotericin B, buspirone, corticosteroids, certain diuretics, fentanyl, losartan, quinidine, rifampin, theophylline, aminophylline, warfarin, cyclosporine, and certain antibiotics.
• The most serious adverse effect is that which affects the liver (hepatitis). Signs of decreased appetite, jaundice, vomiting, or diarrhea should be reported to your veterinarian.
• Compared to some of the other antifungal drugs (amphotericin B, ketoconazole), fluconazole has been associated with fewer adverse effects.
• Fluconazole may cause vomiting, diarrhea, and decreased appetite in dogs and cats.

How Fluconazole Is Supplied

• Fluconazole is available in 50 mg, 100 mg, 150 mg, or 200 mg tablets, or a 10 mg/ml to 40 mg/ml liquid oral suspension.
• Also available as an injectable drug at 2 mg/mL.

Dosing Information of Fluconazole for Dogs and Cats

• Medication should never be administered without first consulting your veterinarian. If you're concerned about costs related to medication, pet insurance may be able to help. Click here to learn more.
• Fluconazole for Dogs: Dosage Chart: The usual dose for dogs is 2.5 to 5 mg per pound (5 to 10 mg/kg) per day orally.
• Fluconazole for Cats: Dosage Chart: The dose for cats is 5 mg per pound (10 mg/kg) twice daily, which often works out to be about 50 mg per cat twice daily orally.
• It is common for fungal infections to require several weeks of treatment.
• The duration of administration depends on the condition being treated, response to the medication, and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.

Additional Considerations When Using Fluconazole in Pets

Fluconazole is particularly valued in veterinary medicine for its ability to penetrate hard-to-reach tissues, including the central nervous system, eyes, and urinary tract. This makes it a preferred choice for treating systemic fungal infections such as cryptococcosis and blastomycosis, which may affect the brain or spinal cord. Its water-soluble nature allows for effective distribution throughout the body, including cerebrospinal fluid, making it more versatile than some other antifungals.

Veterinarians may also prescribe fluconazole for Valley Fever (coccidioidomycosis), a fungal infection prevalent in certain geographic regions like the southwestern United States. In these cases, long-term treatment—sometimes lasting several months—is often necessary, and regular monitoring of liver enzymes is recommended to detect potential hepatotoxicity early.

For pets with compromised kidney or liver function, dosage adjustments may be required. Fluconazole is primarily excreted through the kidneys, so animals with renal impairment may need lower doses or extended dosing intervals. Likewise, pets with liver disease should be monitored closely, as fluconazole can elevate liver enzymes over time.

In addition to oral tablets and suspensions, compounded formulations may be available for pets who have difficulty swallowing pills or require precise dosing. These custom preparations can improve compliance and ensure accurate administration, especially in small dogs or cats.

Owners should be aware that fluconazole is not effective against bacterial, viral, or parasitic infections, and using it inappropriately may delay proper treatment. Always follow your veterinarian’s instructions and avoid self-medicating your pet with human antifungal products.

If your pet is receiving multiple medications, including corticosteroids or antibiotics, discuss potential drug interactions with your vet to avoid adverse effects and ensure optimal therapeutic outcomes.