Dogs and Antifungals

Dec 10, 2021

This is not medical advice. Before pursuing feeding your dog a new food, supplement, or medication it’s advised to consult with your veterinarian.

Fungi and yeast live on your skin and your dog’s skin. They are naturally occurring and generally are not a nuisance. However, if the condition of your dog’s skin changes, or if their immune system is somehow compromised, these naturally occurring organisms can start to grow and cause problems. It is also possible for your dog to contract a nasty fungus from contact with other animals or from being outside. Fungal infections tend to present in two different ways. The first way is systemic, which means the fungal infection is affecting your dog’s body on the inside. The second way is localized, and this is where you see evidence of infection on the outside of your dog, meaning skin, ears, mouth, etc. There are also parasitic fungal infections, like ringworm, which infect the skin. Candida is an example of yeast that can become overgrown. In addition to medication, a change in diet can also help with fungal infections. 

Common Antifungals Medications for Dogs

Here are a few of the common oral anti-fungal medications that your vet may prescribe your dog.

1. Griseofulvin.

Griseofulvin is known by the brand names Fulvicin, Gris-Peg, and Grisovin. This medicine is used to treat localized fungal infections, like ringworms and other infections on the skin and nails. Since this medicine is often used on humans, make sure you follow your vet’s instructions, and not what is listed on the bottle, because those instructions are for humans. Griseofulvin comes in tablet and liquid form and should be given with high-fat foods like cheese, cream, butter, or corn oil. Be sure you measure out the liquid form very carefully. If you happen to be pregnant, avoid contact with this drug by wearing gloves when administering. Also, the liquid form may be safer to administer if you’re pregnant since you will be avoiding breathing in any dust from crushed capsules. This medication may take several weeks to show results. Side effects include vomiting, diarrhea, sensitivity to sunlight, and itchiness. However, when used properly, side effects are uncommon in dogs. 

2. Ketoconazole.

Ketoconazole is an oral antifungal medication. It is also known by the brand name Nizoral. The instructions your vet will give you for this medicine will be different from the instructions on the bottle. Ignore what the bottle says and follow what your vet says to do. This drug can positively impact other medications. It has been used to reduce how much of an expensive drug, like cyclosporine, is needed to be effective. This may become your dog’s favorite medicine, since the tablet form is best given with high-fat foods, like cheese. Butter and cream cheese are also good options for dosing your dog with Ketoconazole. Your vet may also prescribe a liquid form of this medicine, which you squirt into your dog’s mouth. Common side effects include loss of appetite, vomiting, diarrhea, and weight loss. Liver toxicity can also occur. Signs of liver toxicity are severe vomiting and yellowing of the skin and gums. Rare side effects include low platelet count and a change in your dog’s hair or fur color. Cataracts may form after long-term use of this medication. 

3. Itraconazole.

This drug, known by brand names Itrafungol, Sporanox, and Onmel, is a systemic fungal infection medication. It’s used to treat fungal infections in dogs, small mammals, and even exotic animals. Since this is also a medication used to treat humans, its use on animals is known as “off label”, which simply means that your veterinarian will be giving you different instructions for administering this to your dog. These instructions will be different from what it says on the bottle, so be sure you’re able to carefully follow the instructions your vet gives you for this medication. This medicine is given to dogs by mouth in the form of a tablet, capsule, or liquid formulation. While you can give this medicine to your dog with or without food, if there is any stomach upset, like vomiting, give it with food. You’ll likely notice some improvements after a few days, but a complete course of treatment will take a few weeks. It is very common for dogs to lose their appetite on this medication. Other, more serious side effects include sores on the skin (skin lesions that ulcerate or break open), swelling of the extremities, and liver toxicity. Signs of liver toxicity are yellowing of the eyes, skin, or gums, continuous vomiting, bloody or severe diarrhea, pain in the stomach area, and changes in behavior.

4. Fluconazole.

This antifungal medication is most often used to treat yeast fungal infections on the skin, but it can also be used to treat systemic yeast infections as well. Also known by the brand names Diflucan or Trican, you can get a prescription for this medicine from a veterinarian. This drug is often used after another medication has failed to treat a yeast infection. Fluconazole is good for treating more serious infections and has fewer side effects than other medications. It can be used to treat ringworms, but vets tend to reserve it for use against more serious infections like Blastomycosis and Histoplasmosis. Vets will also use this drug to treat internal, or systemic, fungal infections like urinary tract infections or a lung infection from a dog inhaling infected dirt. One reason vets will choose this medication over others is that it is effective at crossing the blood-brain barrier, which means it can go where it is needed more effectively. While this drug is absorbed quickly, it will take a week or two for you to see an improvement in symptoms. A full treatment will likely take several months. Common side effects include diarrhea, vomiting, loss of appetite, dark urine, jaundice, rash, fatigue, anemia, pale gums, tongue or nose, and renal failure.

5. Amphotericin B.

This drug is one of the oldest antifungal drugs and is considered to be the “gold standard”. It acts effectively against a wide range of fungi and yeasts. This drug damages the fungi cells and causes them to die. However, this drug must be given by injection, it is not effective when taken by mouth. It is not as effective for long-term treatments because it needs to be administered by injection. However, it makes a good first start at treatment because it acts so quickly and effectively. Unfortunately, long-term use can be damaging to the kidneys. Make sure your dog is well hydrated before taking them to receive their injection at the vet’s office. Side effects include fever, nausea, and vomiting. 

6. Flucytosine.

This medicine interferes with infectious fungi at the cellular level, stopping their metabolism and their protein productions. This is a well-absorbed drug and is highly effective on yeasts such as candida but has no effects on other fungi. It is used for systemic infections, including urinary tract infections. The infectious yeast can become resistant to this drug. In this case, flucytosine is often paired with amphotericin B. It does have some adverse side effects, such as vomiting, diarrhea, loss of appetite, bone marrow suppression, and skin eruptions. This drug is given by mouth, or by injection at a vet’s office. While it is unknown if this is a safe drug for a pregnant animal, it is not safe for nursing animals. 

7. Terbinafine.

Terbinafine disrupts fungal cells from growing in the early stages. Also, know by the brand name Lamisil, this is an oral drug used to treat both systemic and local fungal infections. It’s important to note that the directions on the bottle may not be accurate. If your vet has prescribed this drug, be sure to follow your vet’s instructions and not the bottle’s. Terbinafine comes in tablets or granules. This medicine is giving by mouth, and with food, to prevent vomiting. It may take a few weeks before to see the full effects of this medicine, but you are likely to notice some improvements gradually after a few days of giving it to your dog. This medication generally doesn’t have any side effects, but there may be some digestive issues such as vomiting, lack of appetite, and diarrhea. Excessive panting and elevated liver enzymes are also a possibility with this medication.

8. Systemic Iodine.

While scientists and doctors don’t know how systemic iodine works, they do know that it works on animals, including dogs, cats, and horses. Dogs are treated with potassium iodide at a dose of 40mg per kilogram of weight. Side effects can occur in small animals, such as vomiting, diarrhea, depression, and lack of appetite. Side effects specific to dogs are discharge from the nose and eyes, scaling (scaly and or crusty skin), and dry hair or coat. In larger animals some side effects that were occasionally seen are coughing, variable appetite, and joint pain. Systemic Iodine should not be used on pregnant animals. 

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