Griseofulvin

Griseofulvin is a fungistatic medication used to treat fungal infections like ringworm which affect the skin and toenails of canines. This medication is usually the second choice for tough cases for which ointments prove ineffective. Griseofulvin is effective against all epidermal funguses which cause ringworm, including Epidermophyton, Microsporum, and Trichophyton. 

This medication targets fungal pathogens in two different ways. Its primary mechanism is to hinder the reproduction of fungal cells. Secondly, griseofulvin creates a barrier on the surface of the skin cells, which prevents pathogens from reaching the vascular dermis and spreading.

Dosage

A typical dose of griseofulvin for dogs is 25 mg per lb, once daily. 

Dosage instructions

Vets recommend giving this medication with a high-fat meal to improve absorption and decrease the chance of stomach upset. Pregnant women and young pet owners should use extreme caution when administering this medication.

Use gloves when handling the capsules and avoid inhaling the contents. A dust mask may be necessary to avoid inhaling griseofulvin powder if you must open the capsules. After disposing of your protective equipment, wash your hands with soap and water for at least 30 seconds.

Efficacy

A Brazilian study of canines with fungal infections found griseofulvin for dogs was 100% effective, with no side effects. The study concluded that griseofulvin took an average of 41 days to completely rid canines of fungal pathogens. 

Griseofulvin also treats a variety of fungal cells that affect the skin, but research shows some funguses can become resistant to this medication over time. 

Side effects

Griseofulvin is considered safe for most dogs, but side effects can occur. These are the most common side effects of griseofulvin for dogs: 

• Sunlight sensitivity

• Stomach upset

• Frequent, loose stools

• Low hemoglobin levels

• Mood changes

• Sunburn

• Decreased bone marrow activity

• Liver damage

• Liver failure

Considerations

Since griseofulvin is a liver microsomal enzyme inducer, it isn't recommended for canines with low liver function. Otherwise, healthy pets who are on this medication for an extended period should have regular vet visits to monitor their liver function. 

Griseofulvin can decrease the effectiveness of cyclosporin and coumarin anticoagulants, so a higher dosage of these medications may be necessary. 

This medication should be avoided in combination with other bone marrow suppressants since combining them can lead to very low red blood cell counts.

Griseofulvin can cause the skin to become more prone to sunburn and irritation. While on this medication, try to avoid subjecting your dog's to natural or artificial UV rays. Apply a dog-safe sunscreen with a high SPF if you know your dog will be exposed to harsh rays.

Drug interactions

Griseofulvin is known to hinder the effects of some drugs and increase the effects of others. Talk to your vet if your pet is on any of the following medications:

• Barbituates

• Cyclosporin

• Coumarin anticoagulants

• Bone marrow suppressants

• Immunosuppressants

• Carbamazepine

• Asprin

• Ketoconazole

• Cephalexin (Keflex)

• Warfarin

• Certain dietary supplements

• Valproic acid

• NSAIDs

• Itraconazole

• Amoxicillin

• Benedryl 

Allergic reactions and sensitivity

Serious and sometimes fatal drug reactions can occur while taking this medication. Call your vet if your dog exhibits abnormal or uncontrollable scratching, blisters of the skin or mucus membranes, peeling skin, rash, or unusual swelling anywhere on the body. 

Frequently asked questions

Can my dog still have vaccines while taking griseofulvin?

Yes. There’s no research indicating any vaccines interact with griseofulvin for dogs. You may continue your pet’s vaccinations according to their schedule unless your vet explicitly says otherwise. Consult your vet if you have any questions.

Can I bathe my dog if they have ringworm?

Yes, bathing a dog with ringworm is perfectly safe if you take appropriate precautions. Ask your vet before using a fungicidal shampoo if your pet is currently taking griseofulvin. Immediately after bathing, wash your hands well with warm water and soap for at least 30 seconds to remove any dermophytes that may have gotten on your hands. Ringworm is contagious to humans, so you must practice good hygiene after petting an infected mammal. 

Is griseofulvin a safe treatment for ringworm in breeding dogs?

Avoid giving griseofulvin to breeding and lactating animals. In males, griseofulvin significantly decreases sperm production. Use of this medication during pregnancy can cause congenital defects and fetal death. 

How long will my dog have to be on griseofulvin?

Griseofulvin is usually given for about a month, but prolonged treatment may be necessary for more stubborn fungal infections. Some dogs have to take this medication for 3 months or more before the infection clears up. 

Is griseofulvin helpful for dogs with bacterial or yeast infections?

No, this medication is only effective against fungal infections. If you suspect your pet has a bacterial or yeast infection, they'll need to see a vet for antibiotics and a different antifungal.