What is ketoconazole?
Ketoconazole (brand name: Nizoral®) is an antifungal medication used to treat fungal infections. Because this drug affects how some other drugs are metabolized, it has also been used to reduce the dosage of expensive drugs such as cyclosporine.
"Many drugs are commonly prescribed for off-label use in veterinary medicine."
Its use in dogs, cats, other small mammals, and reptiles to treat fungal infections is “off label” or “extra label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
How is ketoconazole given?
- Ketoconazole is given by mouth in the form of a tablet.
- It may also be compounded into an oral liquid. Follow the instructions on the label and measure doses carefully.
- It should be given with food and ideally with high-fat foods such as cheese, butter, or cream cheese.
This medication can take a few weeks before full effects are observed, but gradual improvements are usually noticed after a few days.
What if I miss giving my pet the medication?
If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
Are there any potential side effects?
Ketoconazole may cause the following side effects:
- lack of appetite
- vomiting
- diarrhea
- weight loss
- liver toxicity, which may cause severe vomiting, lack of appetite, and a yellowing of the skin and gums
- suppression of cortisol and testosterone levels (evident in the pet’s bloodwork)
Rare side effects include:
- low platelet counts
- haircoat color change
Long-term use of this medication may be associated with cataract formation.
Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.
Are there any risk factors for this medication?
Ketoconazole should NOT BE USED in pets that are allergic to it.
It should be USED WITH EXTREME CAUTION in:
- pregnant pets (use only for a life-threatening infection)
- cats (due to toxic side effects and availability of safer options)
It should be USED WITH CAUTION in pets that:
- have liver disease
- have low platelet counts
- are undergoing stressful events, such as serious illness, surgery, or trauma
- are used for breeding (it can cause temporary infertility)
- nursing (the medication is excreted in milk)
Are there any drug interactions I should be aware of?
The following medications should be used with caution when given with ketoconazole:
- antacids
- antiarrhythmics
- tricyclic antidepressants
- benzodiazepines
- calcium-channel blocking agents
- ciprofloxacin
- cisapride
- corticosteroids
- cyclosporine
- fentanyl
- fluoxetine
- H2 blockers
- hepatotoxic drugs
- ivermectin
- macrolide antibiotics
- methadone, ondansetron
- praziquantel
- proton-pump inhibitors
- sildenafil
- sucralfate
- theophylline
- tramadol
- trazodone
When ketoconazole is combined with cyclosporine, the elimination of cyclosporine is decreased, which allows for a lower dose. This interaction is sometimes created intentionally to decrease the cyclosporine dose needed, especially for large dogs.
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.
Is any monitoring needed with this medication?
- A complete blood count with a focus on platelets should be monitored while using ketoconazole.
- When using this medication long-term, liver enzymes should be monitored every two to three months for the first six months, and then twice yearly thereafter.
- Your pet should be monitored for side effects, paying special attention to signs of low cortisol levels.
- Your veterinarian may monitor your pet to be sure that the medication is working.
How do I store ketoconazole?
This medication should be stored at room temperature, in a dry place protected from moisture.
What should I do in case of emergency?
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.
