(For veterinary information only)
WARNING
The size of the tablet/medication is NOT an indication of a proper dose. Never administer any drug without your veterinarian's input. Serious side effects or death can occur if you use drugs on your pet without your veterinarian's advice.
It is our policy not to give dosing information over the Internet.
Brand Names: Sporonox, Onmel, and Itrafungol
Available in 100 mg capsules, 200 mg tablets, or as an oral solution
Background
The development of oral medications to be used in the treatment of invasive fungal infections has represented an immense medical breakthrough. With oral treatment available, human patients no longer require hospitalization several days per week for intravenous treatment of their disease; a more normal and productive lifestyle is now possible. Further, the toxicity profiles of the newer oral drugs represent a vast improvement over those of the older injectables.
Ketoconazole was the first such oral antifungal drug, but it had room for improvement regarding its side effect potential. There were problems with nausea, liver toxicity, and feminization of male patients. Itraconazole was developed in answer to these concerns. Its potential for side effects is far lower, although its expense, unfortunately, has been problematic.
How this Medication Works
Itraconazole works by inhibiting the fungal enzymes that produce ergosterol, an important component of the fungal cell wall. Without adequate ergosterol, the fungal cell becomes weak, leaky, and ultimately dies.
Fungal infections for which itraconazole can be used include:
Side Effects
The chief reason for choosing itraconazole over other antifungal agents is to avoid side effects over the long treatment courses that are typically needed for the treatment of fungal disease. While itraconazole users do not commonly experience side effects, it is important to be aware of what to watch for, the main issue of concern being liver toxicity.
Side effects of note are appetite loss, vomiting, and/or diarrhea. If they occur, medication should be discontinued, and liver enzymes should be checked. Appetite loss in particular, is felt to be an important sign of toxicity and generally does not occur until itraconazole has been in use for over one month.
If an adverse side effect occurs, it is expected to resolve by discontinuing the medication. After recovery, itraconazole can usually be restarted at a lower dose.
If you think your pet may be having an adverse drug reaction, notify your veterinarian right away.
Itraconazole should not be given to patients with known liver disease if possible. In one research publication, an SGPT/ALT enzyme level of 250 IU/L was felt to be the highest tolerable level compatible with itraconazole use. Approximately five to 10% of dogs receiving standard doses of itraconazole will develop liver disease severe enough to warrant discontinuing the medication. Expect periodic evaluation of liver enzymes (blood testing) to be recommended throughout the duration of itraconazole therapy.
Another side effect worth mentioning is necroulcerative dermatitis, which occurs in 5-10% of dogs receiving itraconazole on the higher end of the recommended dosage spectrum. This reaction leads to a blood vessel inflammation that, in turn, leads to skin ulcers. Discontinuing itraconazole leads to the resolution of this condition, should it arise.
Interactions with Other Drugs
The use of itraconazole in combination with the antacids Pepcid, Zantac, cimetidine (Tagamet), omeprazole (Prilosec), or with the antibiotic rifampin, will lead itraconazole to be less effective. If itraconazole must be used with these medications, it is recommended that at least two hours pass between giving the antacid and the itraconazole.
Serious heart abnormalities have resulted when itraconazole was used with the antihistamine terfenadine (Seldane) or with the intestinal motility modifier cisapride (Propulsid). These medications should not be used with itraconazole.
The following heart medicines will be stronger when used with itraconazole and dosage may need to be reduced: amlodipine, digoxin, warfarin, or quinidine. A similar problem occurs with cyclosporine, an immune suppressant used in immune-mediated disease, allergy, or after an organ transplant. In fact, there is a long list of medications that are made stronger - and potentially more toxic - when combined with itraconazole. Other drugs include glipizide, a treatment for diabetic cats; the benzodiazepine tranquilizers, such as diazepam and alprazolam; anti-anxiety medications buspirone and clomipramine; fentanyl, a narcotic pain reliever; and cyclophosphamide, a chemotherapy agent. Because of this long list of interactions, it is important not to combine any medication with itraconazole without first checking with your veterinarian.
The macrolide antibiotics, such as erythromycin, actually boost itraconazole levels and could increase the potential for itraconazole toxicity.
Itraconazole may increase the toxicity potential of cannabidiol (CBD)-containing products.
Now that brand name Itrafungol suspension has become available in the U.S., warnings about compounded itraconazole are less of a concern. Before the advent of Intrafungol, dosing for smaller animals was challenging as the capsules were too high in strength, and the human oral suspension was so dilute that impractically high volumes were needed. Compounding pharmacies were commonly asked to create oral suspension using bulk itraconazole powder. Such compounded products have poor bioavailability and are best avoided, something that is more easily accomplished now that there is a licensed feline product on the market.
Itraconazole suspension may be given with or without food in cats, but for other species, it is best given with food. Itraconazole capsules are best given with food.
If an itraconazole dose is accidentally skipped, do not double up on the next dose. Simply give the medication when it is remembered or pick it up with the next dose, allowing at least the proper interval between doses according to the label instructions.
Itraconazole is able to penetrate most body tissues and thus fight fungal infections in most organs. It cannot penetrate, however, the blood/brain barrier in the absence of active inflammation and thus is not reliable in central nervous system fungal infections. In such a situation, another closely related medication fluconazole would be helpful.
Fungal infections as a general rule are resistant to treatment, and often months of therapy are needed. It is important not to discontinue treatment prematurely despite the expense.
(An exception might be a Malassezia (yeast dermatitis), which frequently clears up in a couple of weeks.)
Itraconazole is dangerous if given during pregnancy. If a pet is pregnant, itraconazole should be avoided unless the fungal infection in question is potentially life-threatening.
Itraconazole should also be avoided during lactation as it will be delivered via milk to any nursing young.
Itraconazole can reduce the strength of the heart's contractions to an extent that would not be significant in the absence of heart disease. This could, however, be a problem in a patient with reduced heart function.