Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066

(310)391-6741

www.marvistavet.com

FLUCONAZOLE

(for veterinary information only)

BRAND NAME: DIFLUCAN

 

AVAILABLE IN
50 mg, 100 mg, 150 mg, 200 mg
TABLETS
AND ORAL SUSPENSION

 

BACKGROUND

The development of oral medications to be used in the treatment of invasive fungal infections has represented an immense medical breakthrough. With oral treatment available, human patients no longer require hospitalization several days per week for intravenous treatment of their disease; a more normal and productive lifestyle is now possible. Further, the toxicity profiles of the newer oral drugs represent vast improvement over those of the injectables.

Ketoconazole was the first such oral antifungal drug but it had room for improvement regarding its side effect potential. There were problems with nausea, liver toxicity, and feminization of male patients. Fluconazole was developed in answer to these concerns. Its potential for side effects is far lower and, recently, generic medications have made fluconazole readily affordable. Fluconazole represent yet another generation allowing excellent penetration of the blood/brain barrier, allowing neurologic fungal diseases to be treated.

HOW THIS MEDICATION WORKS

Fluconazole works by inhibiting the fungal enzymes that produce “ergosterol,” an important component of the fungal cell wall. Without adequate ergosterol, the fungal cell becomes weak, leaky and ultimately dies.

Fungal infections for which fluconazole can be used include:

  • Dermatophytosis (“ringworm”) though it is usually reserved for
    more serious fungal diseases.

  • Blastomycosis

  • Cryptococcosis (“window washer’s disease")

  • Histoplasmosis

  • Aspergillosis (conflicting agreement as to whether it is effective or not
    against this fungal infection.)

  • Candidiasis

  • Coccidiodomycosis (“Valley Fever”)

  • Malassezia dermatitis (Yeast infection of the skin)

Molecular structure of Ergosterol
(Photocredit: Public Domain Graphic via Wikimedia Commons)

 SIDE EFFECTS

There are three reasons for choosing fluconazole over other antifungal agents. One reason is to avoid side effects, especially with long term use. Another is to penetrate the blood-brain barrier or eye, places where other antifungals cannot go, in order to address a neurologic or ophthalmic infection. Other antifungals are not capable of entering such sequestered areas of the body. The third reason is expense when compared to itraconazole. Itraconazole is frequently the alternative treatment for systemic fungal disease and itraconazole is fraught with bioavailability issues and inconvenient dosing sizes. Fluconazole is available as an effective generic and compounding appropriate pet formulae is not difficult. Itraconazole is "fungicidal," meaning it kills the fungus, while fluconazole is "fungistatic," which means it prevents the fungus from reproducing. The host's immune system must be strong enough to actually kill the fungus when the patient is on fluconazole.

While fluconazole users do not commonly experience side effects, it is important to be aware of what to watch for.  Side effects of concern are appetite loss, vomiting, and/or diarrhea. If they occur, medication should be discontinued and liver enzymes should be checked.

If an adverse side effect occurs, it is expected to resolve with discontinuation of the medication. After recovery, fluconazole can usually be restarted at a lower dose.

IF YOU THINK YOUR PET MAY BE HAVING AN ADVERSE DRUG REACTION,
YOU SHOULD NOTIFY YOUR VETERINARIAN’S OFFICE RIGHT AWAY.

 

INTERACTIONS WITH OTHER DRUGS:

  • The following drugs are stronger in the presence of fluconazole (and thus may have more side effects potential):

  • Buspirone: an antianxiety medication

  • Cisapride: used to improve the motility of the intestinal tract and stomach.

  • Corticosteroids - used for inflammation and to suppress the immune system in numerous scenarios

  • Cyclophosphamide: an agent of chemotherapy

  • Cyclosporine: an immunomodulator used for atopic dermatitis, immune mediated hemolytic anemia, thrombocytopenia, and other immune-mediated diseases (doses of cyclosporine can be decreased 29-50%).

  • Fentanyl: a narcotic pain reliever

  • Non-steroidal Anti-inflammatories - anti-inflammatory pain relievers

  • Quinidine - a heart medication

  • Rifampin - an antibiotic

  • Theophylline: an oral airway dilator

  • Vincristine: an agent of chemotherapy.

 

CONCERNS AND CAUTIONS

  • Fluconazole can be given with or without food.

  • One to two weeks are needed to get a stable blood level of fluconazole. Do not expect rapid results.

  • Fluconazole is removed from the body via the kidneys. If a patient requiring this medication has poor kidney function, dose adjustments will be necessary.

Fluconazole is able to penetrate most body tissues and thus fight fungal infections in most organs.

FUNGAL INFECTIONS AS A GENERAL RULE ARE VERY RESISTANT
TO TREATMENT AND OFTEN MONTHS OF THERAPY ARE NEEDED.

Fluconazole is dangerous if given in pregnancy. If a pet is pregnant, Fluconazole should be avoided unless the fungal infection in question is potentially life-threatening.

Fluconazole should also be avoided in lactation as it will be delivered via milk to any nursing young.

 Page last updated: 9/2/2016