By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Brand Name: Nizoral
Available in 200 mg tablets
Fungal infections are generally resistant to therapy. Treatment is prolonged and often requires months, depending on how deep the infection is and how strong the patient’s immune system is. Fungal infections can be limited to the skin as happens with ringworm or Malassezia dermatitis, or they can involve more crucial organs such as the lung, bone, and even the nervous system. The superficial infections can generally be eradicated in a matter of weeks while the deeper infections may take over a year.
In the past, the only treatment for life-threatening fungal infections was a medication called Amphotericin B. This medication could only be given intravenously in a fluid drip and it was associated with a high incidence of kidney failure (some sources say up to 50%). Obviously, an innovation in treatment was needed. Ketoconazole represents this innovation. Ketoconazole not only is free from renal side effects, but is also given orally as a tablet, sparing patients expensive hospitalization time.
Since ketoconazole’s introduction, related anti-fungals have been released to improve upon its activity. For example, itraconazole was introduced to reduce the incidence of nausea side effects. Fluconazole was developed to improve penetration of the central nervous system and treat fungal infections there. With the introduction of generic forms ketoconazole and its relatives, treatment of fungal disease can be affordable, safer, and more effective.
How this Medication Works
Ketoconazole works by interfering with the structure of the fungal cell wall. Depending on the fungus and depending on the dose used, ketoconazole may kill the fungus or just inhibit its ability to reproduce. Fungal infections for which ketoconazole is commonly used include:
There is another effect of ketoconazole that is generally thought of as a side effect but that can be used as a therapeutic goal. Ketoconazole blocks the synthesis of cortisone in the adrenal gland. This means that ketoconazole can be used to treat Cushing's disease, in which an excessive amount of adrenal hormone is produced.
Ketoconazole can also be used to slow the body's removal of the immunomodulating drug cyclosporine. Cyclosporine is a very expensive medication so using ketoconazole to spare its use may reduce the dose requirement enough to make treatment affordable.
The lethal dose of this medication is at least 50 times the usual recommended dose, thus serious side effects are unusual; nausea and upset stomach are not unusual.
Interactions with Other Drugs
It is better not to give ketoconazole while using antacids because it is better absorbed when there is acid. Sucralfate, another medication used for stomach ulceration, may also interfere with absorption of ketoconazole. Stagger ketoconazole and antacids by a couple of hours if possible.
Cyclosporine, an immune suppressive agents used in transplant patients as well as in certain immune mediated conditions, will have increased blood levels when it is given with ketoconazole. As mentioned, this pharmacological trick can be exploited to reduce the dose of cyclosporine.
Other drugs that may have higher blood levels or stronger effects than normal include: methylprednisolone (a corticosteroid), glipizide (an oral medication for diabetes mellitus), cyclophosphamide (an agent of chemotherapy), ivermectin (in higher doses), vincristine (used in cancer chemotherapy), tramadol (a pain management drug), antianxiety medications (clomipramine, buspirone, trazodone, benzodiazepines such as alprazolam, or amitriptyline) and warfarin (an anticoagulant).
Macrolide antibiotics such as azithromycin and erythromycin can increase ketoconazole concentrations and increase the likelihood of ketoconazole side effects.
When ketoconazole and cisapride are used concurrently, dangerous heart rhythm disturbances can result; these medications should not be used together.
Theophylline, an airway dilator, may be less effective with concurrent use of ketoconazole.
Concerns and Cautions
It is our policy not to give dosing information over the Internet.