Ketoconazole (Nizoral) was one of the first antifungal medications used to treat localized or system fungus infections in dogs. It is available in various forms, including oral tablets and liquid, intravenous solutions, as well as creams and shampoos.
Veterinarians have found ketoconazole effective for a variety of fungal infections, and it may only be used under the direction of and prescribed by a vet. Ketoconazole for dogs is often prescribed for yeast and ringworm infections of the skin. Other common uses include fungal infections in the lungs and central nervous system.
The cost of treating a medium-sized dog (about 45 pounds) with oral ketoconazole is about $.50 a day if given in a typical dose. Topical creams and shampoos cost an average of $15 per container depending on the source and whether the formulation is generic or brand name.
The usual dose of ketoconazole for dogs for most acute fungal and yeast infections is:
Treatment duration is typically six to eight weeks, and the dose is lowered in dogs with liver or kidney function issues. For long-lasting chronic infections, the maintenance dose is between 2.5 and 5 milligrams per kilogram of weight once daily.
Since ketoconazole needs to be in an acidic environment to dissolve properly, doses should be given with food to activate the production of hydrochloric acid in the stomach. For this same reason, the dog should not be on antacids or H2 blocker medications which reduce acid.
Ketoconazole is an imidazole antifungal that is known to be unevenly absorbed and slow to provide therapeutic drug levels. Therefore, it is not generally prescribed alone for use in severe, life-threatening fungal infections such as fungal meningitis or infections in immunocompromised individuals. In these cases, it may be administered intravenously with another medication called amphotericin B.
While ketoconazole for dogs is used less often than newer antifungal medications, it remains reasonably therapeutic for the treatment of flush, or candidiasis, as well as Cryptococcus, (fungal meningitis) Microsporum (ringworm), Malassezia (dermatitis), Coccidioides (Valley Fever), and Blastomyces infections.
Ketoconazole is able to reduce production of corticosteroids by the adrenal gland and has been used in canine Cushing’s Disease. A research study of a group of dogs with hyperadrenocorticism examined the effect of administering ketoconazole, with the result that 90 percent of the dogs experienced reduced corticosteroid levels. However, newer and safer medications like trilostane have been used more frequently in the years since that study.
When treating severe autoimmune diseases with expensive drugs like cyclosporine, studies show that ketoconazole for dogs is able to reduce the amount required for therapeutic results, so it is sometimes seen as a cost-effective treatment adjunct.
There are several side effects that have been reported with ketoconazole, including:
- Decreased appetite
- Weight loss
- Nausea and vomiting
- Hair loss
- Itchy skin
- Temporary infertility in males
- Change in hair color
- Reduced blood platelet count
- Cataracts (with long term use)
- Birth defects
- Liver toxicity
Ketoconazole for dogs should be prescribed with caution in pregnant or nursing females, dogs with liver disease, dogs with severe illness, or with surgery or trauma. Throughout treatment, liver enzymes and platelet count blood tests should be performed.
Ketoconazole (Nizoral) may interact with the following medications and substances:
- Antacids (Alka-Seltzer, Rolaids, Tums, Mylanta, Maalox, Tums, sucralfate)
- Antiarrhythmics (quinidine, digoxin)
- Tricyclic antidepressants (clomipramine, Clomicalm, amitriptyline)
- Benzodiazepines (diazepam, clorazepate, chlordiazepoxide, flurazepam)
- Anti-anxiety medication (buspirone)
- Anti-cancer drugs (busulfan, doxorubicin)
- Antihypertensives (calcium-channel blockers)
- Antibiotics (ciprofloxacin, isoniazid)
- Gastric motility increaser (cisapride)
- Anti-gout medication (colchicine)
- Chemotherapy and immunosuppressives (cyclophosphamide)
- Certain narcotics (fentanyl, methadone, tramadol)
- Antidepressants (fluoxetine, trazodone)
- H2 blockers (cimetidine, famotidine)
- Acid inhibitors (proton pump inhibitors)
- Anticonvulsants (phenytoin)
- Blood thinner (warfarin)
- Vasodilator (sildenafil)
- Anti-asthmatic (theophylline)
Always tell your veterinarian if your dog is taking any medications, supplements or vitamins before starting ketoconazole.
Allergic reactions and sensitivity
As with all medications, there is a chance your dog may develop a sensitivity or allergy to ketoconazole. If, after starting the medication, you notice any of the following symptoms of an allergy, such as swelling, itching or hives, contact your veterinarian immediately.
Frequently asked questions
Do I need a prescription for ketoconazole?
Yes, this medication is only available with a prescription from your veterinarian.
What kind of monitoring will my dog need while on ketoconazole?
Blood tests for platelet counts, cortisone levels, and liver enzymes should be done on a regular basis, about every 2-3 months, to detect adverse effects. In addition, your vet will recommend periodic visits during treatment to assess the effectiveness of the medication.
How do I store ketoconazole?
This medication should be stored in a cool, dry place. Always check the label for storage instructions, or check with your veterinarian.
If my dog appears to be getting better, should I stop the medication?
It’s important to continue giving this medication as it has been prescribed, for as long as your veterinarian orders it. Stopping the drug prematurely may lead to drug-resistant re-infection.
What do I do if I miss a dose?
If you miss a dose, give it as soon as you think of it. If it’s nearly time for the next dose, wait and give the regularly scheduled dose. Do not double up doses of this medication.
What do I do if my dog gets an extra dose?
If your dog accidentally receives an extra dose or more than they should have, contact your veterinarian immediately. If they are not available, contact your nearest emergency veterinary clinic. Signs of an overdose include lethargy, vomiting, loss of appetite and jaundice.
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