By Rania Gollakner, BS, DVM, MPH

What is griseofulvin?

Griseofulvin (brand names: Fulvicin®, Gris-Peg®, Grisovin®) is an antifungal used to treat ringworm and other skin, hair, and nail fungal infections.

Its use in cats, dogs, small mammals, and horses to treat fungal skin infections is often ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.

How is griseofulvin given?

Griseofulvin is given by mouth in the form of a tablet or liquid suspension. Give with fatty food, such as cheese, cream, butter, or corn oil. Measure liquid forms carefully. Pregnant women should wear gloves while giving this medication and wash hands thoroughly after administration; avoid inhaling any dust from split or crushed tablets.

This medication can take up to a few weeks before effects are noted, and at times improvement may not be noted outwardly.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effects include lack of appetite, vomiting, and diarrhea. Other side effects include sunlight sensitivity and itchiness. Serious side effects include abnormal bleeding, pale gums, weakness, incoordination, collapse, fever, yellowing of the skin, eyes, or gums, severe vomiting, continued lack of appetite, severe sleepiness, or severe skin rashes or wounds. At proper dosages, side effects are uncommon in dogs. In cats, however, side effects are more common.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Griseofulvin should not be used in pets that are allergic to it, pregnant pets, breeding males, or pets that have severe liver disease. Do not use in cats with FIV or FeLV; test cats for viral infections prior to starting this medication. It should be used cautiously in kittens as they are more susceptible to side effects. Use griseofulvin cautiously in lactating pets, as safety has not been established; consider using a milk replacer.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with griseofulvin: alcohol, aspirin, cyclosporine, phenobarbital, theophylline, or warfarin.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Your veterinarian may monitor your pet to be sure that the medication is working, primarily by performing fungal cultures. Your veterinarian will likely monitor blood cell counts prior to starting the medication and then every 1-3 weeks during therapy. Liver enzymes may also be monitored. Monitor your pet at home for serious side effects.

How do I store griseofulvin?

Store this medication at room temperature, ideally between 59°F and 86°F (15°C and 30°C) and do not exceed 104°F (40°C). Store in a tight container and protect from light.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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