Ketoconazole in Dogs: Minor and Major Side Effects

Like any drug given to dogs, ketoconazole (brand name Nizoral) can have serious side effects. This is a medication that kills infections caused by fungus. It helps to disintegrate fungal cell walls. This can be used for a wide array of canine fungal infections such as the inappropriately named ringworm, to various yeast infections, some skin infections that are caused by Cushing's disease and to chronic skin infections in some West Highland white terriers.

Ketoconazole is a human medication and not approved for use in pets. However, many vets will prescribe human medications off-label for dogs. By the time a drug goes through the tedious FDA approval process, the dog could be dead, so vets have to improvise. This is why owners need to be aware of side effects. This is also why veterinarians may prescribe corticosteroids in order to counteract the side effects of ketoconazole, according to "The Pill Book Guide to Medication For Your Dog and Cat" (Bantam Books; 1999.)

Minor Side Effects

One strange but not lethal side effect is that a dog's coat may become lighter in color. Usually, the coat color returns to normal once the medication stops.

Slightly more serious are side effects to the digestive system, including vomiting, diarrhea and loss of appetite. Since dogs need to digest this antifungal pill, vomiting it back up or having it fly through the digestive system will not help the dog. Try giving food along with the pill in order to help ease it on through the digestive system.

Another common side effect is the dog will not have as much energy as usual. This is because the sex hormones will not be made in the usual amounts due to the medication and possibly the fungal infection. Any breeding stud dogs may have no interest in mating and may become sterile until they are off of the medication. But if they have a contagious fungal condition like ringworm, they should be kept away from other dogs as much as possible.

Major Side Effects

The worst side effect of ketoconazole is that it could harm the dog's liver. The dog will show symptoms of this with the yellowing of the skin, gums or eyes. The dog also will seem fatigued and may show other symptoms like vomiting. Ketoconazole should not be given to any dogs with known liver problems.

Another crucial symptom to watch for is sudden bleeding from the dog's nose or mouth. This is a very rare symptom; but contact a vet immediately if the dog seems to be bleeding or no known reason or is bleeding far too much for a very minor wound.

Keep a watch on the dog's eyes for any symptoms of cataracts, which is another very rare side effect from kentoconazole.

The medication may also affect a dog's blood sugar levels if the dog is already on medication for diabetes or hypoglycemia.

References:

"The Pill Book Guide to Medication For Your Dog and Cat." Matthew Hoffman, et al. Bantam Books; 1999.

Pet Place. "Kentoconazole (Nizoral.)" Dr. Mark Papich. http://www.petplace.com/drug-library/ketoconazole-nizoral/page1.aspx

Veterinary Partner. "Kentoconazole (Nizoral.)" Wendy C. Brooks, DVM, DipABVP. http://www.veterinarypartner.com/Content.plx?P=A&A=521&S=1&SourceID=52