Itraconazole is an oral antifungal medication used in cats to primarily treat the fungal infection known as ringworm. In this article, you will learn what itraconazole is, how it works, the types of fungal infections it targets, side effects to look out for, and some frequently asked questions.
Itraconazole for Cats Overview
About Itraconazole for Cats
Itraconazole is classified as a fungistatic triazole compound. It works by inhibiting an enzyme that produces part of the fungal cell wall, thereby severely weakening susceptible fungi.
Itraconazole has activity against several types of fungi, including yeasts and dermatophytes, the latter being the causative agents of ringworm of which Microsporum canis is the primary concern in cats. Additional fungi it has efficacy against include Candida spp, Aspergillus, spp, Cryptococcus spp, Histoplasma spp, and Blastomyces spp.
The veterinary product Itrafungol is an oral solution of itraconazole that is labeled for use in cats. Sporonox is a human brand that is also sometimes used.
What Itraconazole Does for Cats
Itraconazole is FDA-approved for use to treat ringworm, or dermatophytosis, in cats. It is caused by Microsporum canis. There are a few species of dermatophyte fungi that can cause ringworm, but Microsporum canis is the most common and principal causative agent in cats. Microsporum canis causes a form of ringworm that is transmissible to both dogs and to humans.
Contrary to its misleading name, ringworm is caused by a fungus. Its common appearance may show up as single or multiple areas of hair loss and crusting on a cat’s skin. It can often be found most especially on the areas of the head, face, and ears. This is because inquisitive cats often pick the fungus up when checking out dark moist locations where it tends to exist naturally. The fungal spores can thrive on surfaces for 12 to 18 months.
Ringworm can also be transmitted through direct contact with another cat or other animal that is currently infected. In cats, especially longhaired ones, a carrier state may also exist and infect other animals or people through contact. This can happen even though no skin lesions or hair loss is visible.
In some cases where single lesions are found, it is common to use a topical cream or lotion containing an antifungal agent.
If multiple lesions are present or if there is concern that a cat may be a carrier, more comprehensive therapy is employed. Itraconazole is one of these therapy options. Other therapy measures include continued use of topical treatments, bathing with antifungal shampoo, or a product called lime sulfur dip.
Treatment of ringworm in cats is typically successful. It still often requires treatment for several weeks to a couple of months.
While an off-label use, itraconazole may also be used for skin infections involving Malassezia yeast fungi that cause skin dermatitis and infections.
There are some less common types of fungal infections in cats that itraconazole may also be used for in an off-label manner. This includes aspergillosis, cryptococcosis, coccidioidomycosis, sporotrichosis, blastomycosis, and histoplasmosis.
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Side Effects of Itraconazole for Cats
Itraconazole’s side effects in cats appear to be dose-dependent. At higher doses, GI side effects may be more likely and severe, and signs of liver toxicity have been reported more often. Cats on higher doses were found to have liver concerns about 30% of the time.
It is common to check liver values while using itraconazole, especially if any signs of a digestive upset have occurred. Because effects are considered dose-dependent, the medication may be discontinued until liver values have returned to normal. It can then be restarted at a lower or less- frequent dose.
Dosage of Itraconazole for Cats
The FDA-approved, labeled dosage for itraconazole (Itrafungol) for cats to treat Microsporum canis is 5 milligrams/kilogram by mouth given once daily for seven days on alternating weeks, This lasts for three treatment cycles.
The veterinary-labeled oral solution Itrafungol can be given with or without food. The human-labeled oral solution (Sporanox) is typically advised to be given without food to aid in better absorption.
How Long a Cat Should Take Itraconazole
Cats are essentially treated on weeks one, three, and five, and left untreated on weeks two and four.
Both of the FDA-approved brands, Itrafungol (approved for cats) and Sporanox (approved for people), appear to have high bioavailability in cats. The human capsules are not absorbed as well in cats and their dosage size will far exceed the needed dose for most cats, making liquid forms more practical and effective.
In general, if ringworm is found on one cat in a household of multiple cats, all cats should receive administration of itraconazole treatment together at the same time. An asymptomatic carrier state in one of the cats is always possible. Treating just one cat can result in a ringworm infection not resolving as expected or being reacquired.
Doses for other types of fungal infections can depend greatly on what organism is present and should be up to a veterinarian’s discretion.
Because ringworm can resemble lots of other skin conditions that are not caused by Microsporum canis, it is very important to always have a diagnosis based on testing by a veterinarian before starting itraconazole.
Fungal infections can take a long time to treat, often requiring several weeks of medication. It is very important to always continue treatment as directed. This is true, even if visible hair loss or other lesions on your cat’s skin and fur appear to have resolved. Continuing treatment at least one month beyond a negative ringworm culture or PCR is the general standard.
Compounded Itraconazole for Cats
Compounding medications are very common in veterinary medicine. This is because it allows us to provide medical therapy for our animal patients by different dosage routes. It also makes dosing easier based on the form of a medication or its flavor.
However, in the case of itraconazole specifically, it is recommended to not use a compounded form. Studies have shown that these forms are far less bioavailable and less effective than FDA-approved brands.
Itrafungol, the FDA-approved brand for cats, also comes with a dosing syringe. The syringe allows for the most accurate dosing in cats. This is important, given the higher risk of side effects with inappropriate doses.
Also Read: Why Is My Cat Not Eating?
Itraconazole is a common antifungal medication used in cats. It is used predominantly to treat cats with ringworm fungal infections that have multiple lesions or a carrier state. Although GI and liver effects can occur, they appear to be very dose-dependent in cats. The FDA-approved brand Itrafungol is recommended for the best efficacy and safety.
Frequently Asked Questions
What does itraconazole treat in cats?
Itraconazole is labeled for use in treating the ringworm/dermatophyte fungus Microsporum canis in cats. The brand Itrafungol is FDA approved for this use in cats. Off-label, itraconazole can be effective in treating a variety of other fungal infections caused by other fungal organisms.
How long does itraconazole take to work in cats?
The FDA-approved brands are highly bioavailable in cats but because the drug has a long half-life, it may not reach appropriate concentrations for up to one week.
For ringworm, most people will see noticeable improvement or even resolution of hair loss, crusting, or other signs after the first month of treatment. However, it is always important to base further treatment on repeat testing to ensure treatment is not discontinued too early, which could lead to recurrence.
Is itraconazole safe for cats?
The brand Itrafungol, which is FDA-approved for cats, appears to be well-tolerated at the appropriate doses. This brand includes a dosing syringe for accurate dosing. Side effects and toxicity of itraconazole appear in cats to be very dose-dependent, highlighting the importance of proper dosing under a veterinarian.
If side effects are seen, it may be possible to discontinue the drug temporarily and restart it at a lower dose or frequency.
How do you give a cat itraconazole?
The most effective dosage form for cats is one of the FDA-approved liquid solutions. Capsule forms are much less bioavailable in cats, and compounded forms of the medication have also proved to be less effective from decreased absorption.
The liquid solution approved for cats can be given with or without food, meaning that it could be given directly by mouth using the included syringe, or potentially directly on food if a cat will eat it shortly after.
It has been noted that the FDA-approved human brand Sporanox is better given without food, meaning this solution form is best given directly by mouth at least one hour before or after a meal, for best absorption.