Griseofulvin (Fulvicin) for Dogs: An Antifungal Medication for Treating Ringworm
Key takeaways:
Griseofulvin (Fulvicin, Gris-PEG) is an antifungal medication occasionally prescribed for dogs with ringworm fungal infections.
Veterinarians don’t prescribe this medication very often to dogs anymore. And the version for dogs is no longer marketed for use in the U.S.
The most common side effects of griseofulvin for dogs include vomiting, diarrhea, and poor appetite.
Table of contents
Griseofulvin (Fulvicin, Gris-PEG) is an antifungal medication. It isn't prescribed for dogs in the U.S. very often. Learn why this is the case, as well as more details about griseofulvin for dogs below.
Griseofulvin for dogs at a glance
Common names | Griseofulvin (Fulvicin, Gris-PEG) |
What it treats | Ringworm fungal infections |
How it comes (forms) | Tablets |
Common side effects | Lack of appetite, vomiting, diarrhea |
Estimated average cost | $82-$100, depending on the dosage |
What is griseofulvin for dogs and how does it work?
Griseofulvin is an antifungal medication for dogs. Griseofulvin only works against the types of fungi that cause ringworm (also called dermatophytosis). This includes the fungal species that belong to the Microsporum, Trichophyton, and Epidermophyton genera. Griseofulvin doesn’t work against any other fungal organisms or bacteria.
Griseofulvin works by disrupting a fungal cell’s ability to divide, or replicate. This can stop the infection from spreading.
Search and compare options
Griseofulvin only reaches effective concentrations in new hair or toenail growth. This makes it slower to treat ringworm in dogs compared to other available antifungal medications.
What is griseofulvin used for in dogs?
Griseofulvin is sometimes used to treat dogs for the fungal infection ringworm. As mentioned, this is the only type of infection griseofulvin is capable of treating.
Vets used to prescribe griseofulvin more often.But the FDA-approved medications specifically for dogs are no longer on the market in the U.S.
Some of the reasons for griseofulvin’s removal from the U.S. veterinary market include:
The medication has a disagreeable taste to dogs.
Gastrointestinal side effects related to griseofulvin are common.
There are two types of tablets that come in different doses and are not interchangeable. This can be confusing.
It has limited use since it only works against fungi that cause ringworm.
Other antifungal medications that are currently available for dogs are safer and more effective.
More common antifungal medications have now replaced griseofulvin for dogs, including azole antifungals and terbinafine.
Read more like this
Explore these related articles, suggested for readers like you.
How is griseofulvin given to dogs and what is the standard dosage?
The FDA-approved oral tablets of griseofulvin for dogs are no longer available in the U.S. But generic tablets labeled for people can be prescribed off-label for dogs. Prescribing medications off-label is common in veterinary medicine.
Griseofulvin comes in two types of tablets with different doses:
Microsize tablets that contain either 250 mg or 500 mg of griseofulvin
Ultramicrosize tablets that contain either 125 mg or 250 mg of griseofulvin
These dose sizes are not interchangeable. If your dog is changing from the microsize to the ultramicrosize tablets, for example, a veterinarian has to calculate the new dose based on your dog’s weight.
Both types of tablets should be given with or immediately following a fatty meal. This helps with the medication’s absorption into your dog’s body.
Griseofulvin is most often given to dogs once a day. But you can also divide your dog’s daily dose and give it to them every 12 hours. This may reduce digestive side effects.
Because the human tablets are not designed for dogs, they may not be appropriate for your dog as is, given the amount of medication they contain. In this case, your veterinarian may prescribe griseofulvin through a compounding pharmacy. This helps ensure your dog gets the accurate dosage and may also help improve the medication’s taste.
What are the common side effects of griseofulvin in dogs?
The most common side effects of griseofulvin for dogs include:
Lack of appetite
Vomiting
Diarrhea
What are the most serious risks of griseofulvin for dogs?
Less common but more serious effects of griseofulvin for dogs include:
Low red blood cell count
Low white blood cell count
Low platelet count
Poor balance when walking
Liver damage, which may cause yellowing of skin, eyes, and gums
Dermatitis (skin inflammation)
Being more sensitive to sunlight
Toxic epidermal necrolysis (a rare, life-threatening skin reaction)
Griseofulvin can also cause birth defects and defects in young, growing animals. Do not give griseofulvin to pregnant animals or dogs less than 12 weeks old. And if you are pregnant, do not handle griseofulvin because of these effects.
If you are concerned your dog received an overdose of griseofulvin or is having serious side effects, contact:
Your veterinarian
Does griseofulvin interact with any other dog medications?
Griseofulvin can have negative interactions with some other medications your dog may be taking, including:
Aminophylline
Aspirin
Cyclosporin
Estrogens (estriol/incurin)
Theophylline
Warfarin
This does not mean these medications cannot be taken with griseofulvin. But there can be risks of combining them. Always discuss the potential risks, versus the benefits, of medications with your veterinarian.
What should you do if your dog misses a dose of griseofulvin?
If you’re giving your dog griseofulvin every 24 hours and you miss a dose by less than 8 to 12 hours, give them the missed dose. Then, for future doses, give them the medication based on this timing change.
If you missed your dog’s dose of griseofulvin by more than 12 hours, wait until it’s time for the next dose.
If you’re giving your dog the medication every 12 hours and you miss a dose by less than 4 to 6 hours, give them the missed dose. If you missed the dose by more than 6 hours, skip the missed dose and wait until the next one.
Make sure to contact your veterinarian if you need to clarify anything about the timing of doses.
The bottom line
Griseofulvin (Fulvicin, Gris-PEG) is an antifungal medication that treats ringworm fungal infections in dogs. Other antifungal medications have replaced griseofulvin as a preferred treatment for ringworm in dogs. But vets may still prescribe it in some cases.
If your dog is prescribed griseofulvin, look out for side effects such as vomiting, diarrhea, and lack of appetite. Contact your veterinarian if you have any questions about your dog’s medication.
Why trust our experts?
References
Brooks, W. (2021). Griseofulvin (Fulvicin). Veterinary Partner.
Mercer, M. A. (2022). Griseofulvin for use in animals. Merck Manual Veterinary Manual.
Plumb's Veterinary Medication Guides. (2019). Griseofulvin.
Sannat, C., et al. (2019). Isolation of Microsporum canis from dog and its therapeutic management. Journal of Entomology and Zoology Studies.
