Fluconazole
(floo-kon-a-zole)

• Description: Antifungal
• Other Names for this Medication: Diflucan®

Fluconazole is a medication that is used to treat a variety of fungal infections in small animals, birds, and horses. The FDA has approved this drug for use in humans, but it is not officially approved for use in animals. The FDA allows veterinarians to prescribe products containing this drug in different species or for other conditions in certain situations. You and your veterinarian can discuss why this drug is the most appropriate choice.

• Oral antifungal drug used in several species.
• May give with or without food. If your animal vomits or acts sick after receiving the drug on an empty stomach, try giving the next dose with food or a small treat.
• If vomiting continues, contact your veterinarian. Most likely side effects are gastrointestinal related (eg, vomiting, diarrhea, lack of appetite).
• Liver toxicity is possible, but very rare.
• Do not skip doses.

Prescriber Highlights:

• Oral or parenteral antifungal agent particularly useful for CNS infections. Systemic mycoses may require treatment over several months.
• May be effective for treatment of dermatophytosis, onychomycosis, candidiasis, and Malassezia spp dermatitis
• Similar efficacy as itraconazole; however, fluconazole does not require an acidic environment for PO absorption. Can be given with or without food
• Caution is advised in patients with chronic kidney disease, pregnancy, and hepatic failure.
• Adverse effects include occasional GI effects (eg, inappetence, vomiting, diarrhea) in cats and dogs; increased liver enzyme activity and, rarely, severe hepatotoxicity may be seen.
• Many drug interactions are possible.
• The National Institute for Occupational Safety and Health (NIOSH) classifies fluconazole as a hazardous drug; use appropriate precautions when handling.

Uses/Indications:

Fluconazole is used in the treatment of systemic mycoses, including cryptococcal meningitis, blastomycosis, and histoplasmosis. A retrospective study in dogs with blastomycosis found there was no significant difference in efficacy between fluconazole and itraconazole, and although treatment with fluconazole was longer than with itraconazole (ie, median of 183 vs 138 days), fluconazole treatment costs were ≈? less than itraconazole. Similarly, another retrospective study found no difference in efficacy between fluconazole and itraconazole in dogs with histoplasmosis.

Fluconazole may also be useful for superficial skin infections and nail disease associated with candidiasis or dermatophytosis. One study in dogs showed that fluconazole appears to be at least as effective as ketoconazole for the treatment of Malassezia spp dermatitis,3 but other studies have stated fluconazole may not be as effective as ketoconazole or itraconazole. Because of the drug’s unique pharmacokinetic qualities, it is probably more useful in treating CNS or urinary tract fungal infections than other azole derivatives. Unlike ketoconazole, fluconazole does not have appreciable effects on steroid hormone synthesis and may have fewer adverse effects in small animals. Similarly, fluconazole impairs hepatic drug metabolism to a lesser extent than ketoconazole.

What are the side effects of this medication?

In small animals, fluconazole is usually tolerated well, butthere has not been much experience with the drug in animals.

Side effects that usually are not serious include: 

• Lack of appetite, vomiting, diarrhea. You don’t have to be overly concerned if you see any of these signs unless they are severe, worsen, or continue to be a problem.

Contact your veterinarian if this happens.

Side effects that may be serious or indicate a serious problem: 

• Vomiting, severe or bloody diarrhea, lack of appetite, jaundice (yellowing of eyes, skin, or gums), tender or painful abdomen (stomach), bleeding, seizures (convulsions), or severe changes in behavior may indicate liver toxicity (very rare).

If you see any of these signs, contact your veterinarian immediately.

If you have any other questions about this medication, contact your veterinarian or pharmacist.

Precautions/Warnings:

Fluconazole should not be used in patients hypersensitive to it or other azole antifungal agents. In humans, fluconazole is contraindicated in patients receiving drugs that both prolong the QTc interval and are metabolized by cytochrome P450 3A4; significance in animals is unknown (see Drug Interactions). As fluconazole may cause hepatotoxicity (rarely, and less than itraconazole or ketoconazole), this drug should only be used in patients with hepatic impairment when the potential benefits outweigh the risks. Fluconazole is eliminated primarily by the kidneys, so dosages may need to be adjusted in patients with renal impairment. Fluconazole has been associated with prolongation of the QT interval and should be used with caution in patients at increased risk for arrhythmias (eg structural heart disease, heart failure, electrolyte imbalance).

Humans receiving fluconazole for 28 days for treatment of coccidioidomycosis experienced adverse effects (eg, dry skin, alopecia, fatigue, nausea and vomiting), with ≈? requiring therapy changes.

Fluconazole is reportedly both ineffective and highly toxic to budgerigars at typical doses.

The National Institute for Occupational Safety and Health (NIOSH) classifies fluconazole as a hazardous drug; personal protective equipment (PPE) should be used accordingly to minimize the risk for exposure.