Griseofulvin for Horses

PetMD’s medication content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What Is Griseofulvin for Horses?

Griseofulvin is a prescription medication that treats dermatophytosis in horses, commonly known as ringworm fungal skin infection.

Griseofulvin is FDA-approved for use in horses and dogs but is used off-label in other species, including rats, hamsters, guinea pigs, ferrets, and rarely, cats.

Off-label use refers to the practice of prescribing a medication for a purpose different from what it was originally approved for by regulatory agencies like the Food and Drug Administration.

Because effective topical treatments such as shampoos, dips, and sprays are available to treat ringworm fungal skin infections, oral treatment with griseofulvin is less commonly used in horses. Your veterinarian will determine whether this medication is right for your horse.

Griseofulvin is not given to mares during the early stages of pregnancy due to the risk of birth defects, but it is considered safe for mares in the later stages of pregnancy.

In certain circumstances, your vet may recommend a compounded formulation of griseofulvin. Griseofulvin is available for horses as a compounded oral paste and as a compounded powder to put on top of feed.

Compounded medications are prescribed if there’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if your pet has trouble taking pills in capsule form, the dosage strength is not commercially available, or the pet is allergic to an ingredient in the FDA-approved medication. Compounded medications are not FDA-approved.

They are created by either a veterinarian or a licensed pharmacist on an individual basis to best suit a patient’s particular needs. You can learn more about compounded medications here.

How Griseofulvin Works in Horses

Griseofulvin works by blocking the fungal organism from multiplying, thereby preventing the spread of fungal infection onto surrounding skin and hair.

Since griseofulvin does not directly kill the fungus, it is not a true antifungal medication. Treatment with griseofulvin helps shorten the animal’s recovery time and it helps the animal’s infected hairs be less contagious.

Griseofulvin Directions for Horses

Follow the directions on the drug label or as provided by your veterinarian.

Your veterinarian may generally recommend treatment with griseofulvin once a day for a few weeks. Always wear gloves while administering griseofulvin.

Women who are pregnant or who may become pregnant should avoid contact with this medication.

Missed a Dose?

Speak with your veterinarian about what to do if you forget to give a dose of griseofulvin. Generally, they may advise you to give it when you remember, or if it is almost time for your horse’s next dose, to skip the missed dose and resume your normal dosing schedule. Do not give extra or double doses.

Possible Side Effects of Griseofulvin in Horses

Griseofulvin is generally well tolerated in horses. Possible side effects may include:

• Digestive upset (decreased appetite, diarrhea)

• Depression (low energy)

• Decreased red blood cell production, resulting in anemia

• Liver irritation

Human Side Effects

Griseofulvin is also a prescription medication for humans, frequently with dosages different from those prescribed for your horse by a veterinarian.

Due to possible side effects, humans should never use medicine dispensed for their pets and pets should not be given any medicine dispensed for a human’s use. Always wear gloves while administering griseofulvin to your horse.

Women who are pregnant or who may become pregnant should avoid contact with this medication.

If you accidentally ingest an animal medication, call your physician or the national Poison Control Center hotline at (800) 222-1222.

Call Your Vet If:

• Severe side effects are seen (see above)

• Your horse’s condition worsens or does not improve with treatment

• You see or suspect an overdose

• You have additional questions or concerns about the use of griseofulvin

Griseofulvin Overdose Information for Horses

At the time of this publication, studies had not been performed to evaluate the toxicity of griseofulvin in horses.

If you suspect an overdose, immediately contact your veterinarian or an animal poison control center. Consultation fees often apply.

Pet Poison Helpline (855) 764-7661

ASPCA Animal Poison Control (888) 426-4435

Griseofulvin Storage for Horses

Always confirm storage temperatures by reading the prescription label. Griseofulvin should be stored at controlled room temperatures from 68 to 77 F. Keep the container tightly closed in order to protect the medication from moisture and light.

Compounded medications should be stored according to the compounding pharmacy’s label. Keep out of reach of children and pets.

No vet writer or qualified reviewer has received any compensation from the manufacturer of the medication as part of creating this article. All content contained in this article is sourced from public sources or the manufacturer.