Griseofulvin for Cats: A Less-Common Medication for Ringworm
Key takeaways:
Griseofulvin is an antifungal medication that can be used to treat ringworm infections in cats.
Most side effects are mild, but serious side effects can occur. Risks include bone marrow suppression, neurological diseases, and low white blood cell count.
Your vet may choose griseofulvin to treat ringworm in your cat. But it isn’t as commonly prescribed anymore because there are better options.
Table of contents
Griseofulvin is one of several medications that can be used to treat ringworm in cats.
Although the name “ringworm” suggests that this infection is caused by a worm, ringworm is actually a fungal infection. Infected cats typically develop round or ring-shaped areas of hair loss. This infection is most common in kittens, due to their immature immune systems. But it can also affect adult cats.
Ringworm spreads through contact with an infected cat, a contaminated object, or a contaminated environment. Some ringworm infections clear on their own, but many need antifungal treatment.
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Griseofulvin for cats at a glance
Common names | Griseofulvin (Fulvicin, Gris-PEG) |
What it treats | Ringworm |
How it comes (forms) | Tablet, oral liquid |
Common side effects | Vomiting, diarrhea, nausea, lack of appetite |
Average cost | $82-$100, depending on the dosage |
What is griseofulvin used for in cats?
Griseofulvin (Fulvicin, Gris-PEG) is an antifungal medication. It is most commonly used in cats to treat ringworm, a fungal infection of the skin. The medication works by stopping a fungal infection from reproducing and spreading.
Veterinarians also sometimes use griseofulvin to treat other fungal infections of the skin and nails. But veterinarians typically don’t prescribe griseofulvin to cats for any reason nowadays. That’s because other medications have been found to be just as effective but with fewer side effects.
How is griseofulvin dosed and given to cats?
Griseofulvin is given by mouth, as a tablet or as a liquid suspension. Giving the medication with food can improve absorption.
Griseofulvin is usually given once or twice daily. Less commonly, your veterinarian may recommend a high dose of griseofulvin once weekly. They will determine the best griseofulvin dose for your cat based on its body weight and other factors.
Your cat may need weeks or even months of treatment for a fungal infection. Your veterinarian will monitor your cat carefully during treatment. In the case of ringworm, treatment is continued until tests verify that the infection has been cleared.
Follow your veterinarian’s dosing recommendations carefully to reduce the risk of side effects.
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What are the common side effects of griseofulvin in cats?
The most common side effects of griseofulvin are usually digestive in nature. Gastrointestinal effects of griseofulvin include:
Decreased appetite
Nausea
Vomiting
Diarrhea
If your cat develops digestive side effects while taking griseofulvin, contact your veterinarian for guidance.
What are the most serious risks of griseofulvin?
While most griseofulvin side effects are mild, serious effects can occur. The most serious side effects seen in cats include:
Anemia
Low white blood cell count
Weakened immune system
Increased bleeding
Liver toxicity
Neurological disease
Skin rashes
Sensitivity to sunlight
Fortunately, these effects are rare. Your veterinarian will monitor your cat closely during griseofulvin treatment, so any serious effects can be identified and addressed.
Some of these side effects are more common in cats infected with feline immunodeficiency virus (FIV). These cats already have a weakened immune system and low white blood cell counts. This puts them at higher risk of side effects from griseofulvin. Cats with feline leukemia virus (FeLV) may also be at higher risk of serious side effects. Therefore, veterinarians typically avoid using griseofulvin in cats with FIV or FeLV.
You also shouldn’t give griseofulvin to pregnant cats, because it may cause birth defects. Griseofulvin should also be avoided in nursing cats.
Does griseofulvin interact with any other cat medications?
Griseofulvin can interact with a number of common medications for cats. These include:
Aminophylline
Cyclosporine
Estrogens (estriol/incurin)
Phenobarbital
Theophylline
Warfarin
In some cases, griseofulvin increases the effect of other medications. This could raise the risk of side effects. In other cases, griseofulvin interferes with other medications, which could lead to the other medication not working as expected. Either of these interactions could have significant consequences for your cat.
Be sure your veterinarian is aware of any medications your cat is taking. This includes prescription medications, over-the-counter medications, and herbal supplements. Your veterinarian will take these other medications into account before prescribing griseofulvin.
What should you do if your cat misses a dose of griseofulvin?
If your cat misses a dose of griseofulvin, give the missed dose as soon as possible. If it’s almost time for your cat’s next dose, skip the missed dose and give the next dose as scheduled.
Do not give your cat two doses of griseofulvin at the same time.
The bottom line
Griseofulvin is a medication sometimes prescribed to cats to treat ringworm. However, it’s not usually the first choice for cats anymore. Other medications for ringworm work just as well and may have fewer side effects.
Although the side effects of griseofulvin may sound worrisome, serious effects are rare. Your veterinarian will work with you to minimize those effects. If your veterinarian has prescribed griseofulvin for your cat, they feel that the benefits of treatment outweigh the risks.
Work closely with your veterinarian during treatment, monitoring your cat carefully. Look for potential side effects and for evidence that its infection is getting better.
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References
Brooks, W. (2001). Griseofulvin (Fulvicin). Veterinary Partner.
Cornell Feline Health Center. (2016). Feline leukemia virus.
DeBoer, D. J., et al. (2010). Ringworm in cats. World Small Animal Veterinary Association World Congress Proceedings, 2010.
Rottman, J. B., et al. (1991). Bone marrow hypoplasia in a cat treated with griseofulvin. Journal of the American Veterinary Medical Association.
Scott, F. W., et al. (1975). Teratogenesis in cats associated with griseofulvin therapy. Teratology.
Shelton, G. H., et al. (1990). Severe neutropenia associated with griseofulvin therapy in cats with feline immunodeficiency virus infection. Journal of Veterinary Internal Medicine.
