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Ketoconazole 101: What to Know if Your Dog is Prescribed Ketoconazole

Developed in collaboration with Ernie Ward, DVM

Last reviewed: 1/30/2024

What is Ketoconazole?

Ketoconazole is in a class of antifungal medications called imidazoles. It is most commonly prescribed by veterinarians to treat fungal infections like ringworm (Malassezia dermatitis), fungal ear infections (Malassezia pachydermatis), and skin (dermatophyte) infections. It is also prescribed to treat some life-threatening systemic fungal infections in dogs, particularly Valley Fever (coccidioidomycosis). It is also used to treat Cushing's disease (hyperadrenocorticism) and other superficial yeast infections.

While ketoconazole has been utilized in cats, there is evidence suggesting potential liver toxicity linked to its usage. As a result, other antifungal medications like Itraconazole are more commonly recommended for cats.

Because ketoconazole affects how other drugs are metabolized, it is sometimes prescribed to reduce the dosage of more expensive drugs like cyclosporine.

Ketoconazole comes in oral and topical forms. Your veterinarian may prescribe ketoconazole under the brand name Nizoral®.

Key Facts
  • Ketoconazole is an antifungal medication used to treat fungal infections in dogs.
  • It works by interacting with the formation of the fungal cell wall and inhibits the growth of fungal organisms.
  • It is often prescribed to treat serious, life-threatening systemic fungal infections like Valley Fever and Blastomycosis (Blastomyces dermatitidis or “Blasto”).
  • The most common side effects of ketoconazole in dogs are stomach upset, nausea, vomiting, and loss of appetite.
  • It is not recommended for use in cats.
  • There are a large number of possible drug interactions with ketoconazole. Be sure to talk with your veterinarian about other drugs or supplements your pet is taking.
  • Ketoconazole is available in several oral and topical forms.

How Ketoconazole Works

Ketoconazole works by interacting with the formation of the fungal cell wall and inhibits the growth of fungal organisms. Ketoconazole has also been shown to block the production of corticosteroids by the adrenal gland, has some anti-inflammatory properties, and can suppress T-lymphocyte production.

Ketoconazole is often prescribed to treat systemic fungal infections like Valley Fever and Blasto (Blastomycosis). These types of infections are serious and life-threatening in dogs. They often require prolonged treatment. Some dogs need ketoconazole treatment for up to a year and, in some cases, must remain on it for life. Critically ill pets may start ketoconazole treatment in a hospital to allow a second intravenous antifungal called Amphotericin B to be used concurrently. 

Ketoconazole is not effective against other types of infections caused by viruses, bacteria, or parasites.

Some of the fungi and yeast ketoconazole are used to treat include Blastomyces, Coccidioides, Cryptococcus, Histoplasma, Microsporum, Trichophyton, Malassezia pachydermatis, Candida, Sporotrichosis, and Aspergillus.

Possible Side Effects of Ketoconazole

The most common side effects of ketoconazole in dogs are upset stomach, nausea, vomiting, and loss of appetite. These may be manageable through decreasing or dividing the dose or administering the ketoconazole with a meal.

More severe side effects include increased liver enzyme levels. If your dog experiences anorexia (not eating for 48 hours), vomiting, and diarrhea, contact your veterinarian immediately.

Less common side effects are liver toxicity (especially in cats), decreased platelet count, and temporary lightening of the hair coat.

The use of ketoconazole in cats is generally not recommended. Cats are more likely than dogs to experience side effects, particularly GI upset and hepatotoxicity (liver damage).

Drug Interactions

There are a large number of possible drug interactions with ketoconazole. The following includes those that have been reported or are theoretical. Tell your veterinarian about any other medications or supplements you give your dog before beginning ketoconazole.

Alcohol, antacids, antidepressants, benzodiazepines, Buspirone, Busulfan, calcium channel blockers, Cisapride, corticosteroids, Cyclophosphamide, Cyclosporine, Digoxin, Fentanyl, H2 Blockers, drugs that affect liver function, Isoniazid, Ivermectin, Macrolide antibiotics, Mitotane, Phenytoin, Omeprazole, Quinidine, Rifampin, Sucralfate, some anti-diabetic drugs, Theophylline, Vincristine, Warfarin.

Ketoconazole Dosage Forms and Strengths

Ketoconazole is given orally or applied topically. Dosing is determined by your dog’s body size and weight, type of infection, and any preexisting medical conditions or issues. Be sure to follow your veterinarian’s directions carefully.

Wedgewood Pharmacy provides medication options that help ensure accurate dosing, especially for hard to medicate pets. Click below for a complete list of Wedgewood’s dosing forms and strengths.


What To Do if You Miss a Dose

If you miss giving your pet a dose of ketoconazole, give the next dose as soon as you remember or, if it is close to the next scheduled dose, return to the regular schedule. Do not give your pet two doses (double dose) to catch up. If you are not sure what to do, call your veterinarian.

What to Do in the Case of a Ketoconazole Overdose

Give or apply ketoconazole exactly as your veterinarian prescribes. Contact your veterinarian immediately if you suspect an overdose.

If you suspect your pet or another animal has accidentally overdosed or has eaten this medication inadvertently, immediately contact your veterinarian or the A.S.P.C.A.’s Animal Poison Control Center at 888-426-4435.

Remember to take your prescription container with you when you take your pet for emergency treatment. If you or someone else has ingested this medication, call the National Capital Poison Center at 800-222-1222.

Cost of Ketoconazole

Wedgewood Pharmacy’s ketoconazole preparations start at $0.17 per dose. Your veterinarian will prescribe a specific dosage based on the pet’s weight, condition, and other factors. 

Compounded medicines are prepared for the exact strength your veterinarian prescribes. The price of the medication will depend on the dosage and the medication form, with certain dosage forms and higher strengths generally being more expensive. 

In addition, the cost of a medication will depend upon the price of the other active pharmaceutical ingredients and may increase the cost of the finished drug.

Looking for Ketoconazole

Looking for Ketoconazole?

We can let your veterinarian know that you are interested in our compounded Ketoconazole.

Frequently Asked Questions

Frequently Asked Questions for Ketoconazole

What Does Ketoconazole Do for Dogs?

Ketoconazole is one of the first antifungal medications used to treat localized or systemic fungal infections in dogs. It is available in various forms, including oral tablets and liquids, intravenous solutions (IV), and topical creams and shampoos for skin and ear conditions.

Veterinarians often prescribe ketoconazole for a variety of fungal infections including yeast and ringworm infections of the skin. Other common uses include fungal infections in the lungs and central nervous system.

Does Ketoconazole Interact with Other Medicines?

Yes. There are a large number of possible drug interactions with ketoconazole. Ketoconazole is a potent inhibitor of hepatic enzymes, so dosage adjustments may be necessary to prevent adverse drug interactions. Tell your veterinarian about any other medications or supplements you give your dog before beginning ketoconazole.

How Quickly Does Ketoconazole Work in Dogs?

Ketoconazole should be given with food to improve absorption. When using ketoconazole to treat one of the severe systemic fungal infections, it may take 10-14 days before a noticeable clinical response.

When ketoconazole is used to treat dermatitis caused by a yeast infection, therapeutic shampoos are generally used in addition to the ketoconazole. Treatment may last from 2 to 4 weeks.

Does Ketoconazole Stop Itching?

Ketoconazole shampoo is used to control flaking, scaling, and itching from dead skin cells. Ketoconazole is in a class of antifungal medications called imidazoles. It works by slowing the growth of fungi that cause infection.

Does Ketoconazole Make Dogs Sleepy?

Generally, no. The most-common side effects of ketoconazole in dogs are nausea, vomiting, and loss of appetite. If these side effects are severe or persist beyond 48 hours, notify your veterinarian.

Can Dogs Lick Ketoconazole Antifungal Ointment?

All creams, ointments, and lotions are for external use only. It is important to prevent your dog from licking and swallowing any of these external preparations. They often contain ingredients that could be harmful if swallowed.

How Long Should a Dog Be on Antifungal Medication?

Certain diseases require a dog to be on antifungal medications for a long time, averaging 6 to 12 months. Dogs with disseminated diseases in bones, skin, or internal organs usually require even longer courses of antifungals.

Is Dog Skin Fungus Contagious?

Fungal dermatitis or skin and ear infections are not contagious. Skin fungal infections can recur unless the underlying skin condition or allergy is controlled with medication.

Is Ketoconazole an Antibiotic?

No. It belongs to a group of medications called antifungals. It is used to treat fungal or yeast infections. It will not treat infections caused by bacteria or viruses.

What Is the “Fatal Fungus” in Dogs?

Some people call Blastomycosis the “fatal fungus” in dogs. Blastomycosis or “Blasto” is a fungal disease in dogs caused by inhaling spores from Blastomyces dermatitidis. Dogs contract the infection by breathing in these fungal spores in their environment. When infected, dogs typically experience severe illness, often with respiratory issues, and without treatment, most will not survive. Blastomycosis is a common fungal infection in dogs, and humans can also get infected in the same way as dogs.

What is Valley Fever?

Valley fever is a disease caused by a fungus known as Coccidiodes immitis. The disease is contracted by inhaling fungal spores. Dogs are susceptible because they sniff the ground where they inhale the spores. When the spores are inhaled, they transform into a yeast-like organism that infects the lungs.

This article is meant to provide general and not medical advice. We strongly recommend that a veterinarian be consulted for the specific medical needs of your animal.


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