Voriconazole
Also known as: Vfend
**Voriconazole** is an advanced antifungal medication used for severe or resistant fungal infections. * **Investigational Use**: This drug is relatively new in veterinary medicine, and its use is often considered investigational. It is also quite expensive. * **Administration**: Give the medication at least one hour before or one hour after feeding to ensure proper absorption. * **Adverse Effects to Watch For**: Because experience with this drug in pets is limited, monitor your pet closely. **Contact your veterinarian immediately** if you notice: * Itching or skin rashes * Yellowing of the whites of the eyes or gums (jaundice) * Reduced appetite or weight loss * Difficulty walking, stumbling, or weakness (especially in the hind legs) * Vision problems or dilated pupils * **Cats**: Cats are particularly sensitive to this medication. Watch them extremely closely for any changes in behavior, appetite, or mobility.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Orbital aspergillosis
- Aspergillosis
- General / Pharmacokinetic study
- Avian aspergillosis
- Coccidioidomycosis
How it is given
Possible side effects
- Dogs: Liver enlargement, significant increase in cytochrome P450 hepatic enzymes
- Cats: Azotemia, inappetence, lethargy, weight loss, cutaneous drug reactions, ataxia, hind limb paresis/paraplegia, visual signs (mydriasis, decreased PLR), arrhythmias, hypokalemia
- Humans: Visual disturbances (blurring, spots, wavy lines), rashes, GI effects (nausea, vomiting, diarrhea), hepatotoxicity, hypertension/hypotension, tachycardia, peripheral edema, hypokalemia, hypomagnesemia
- Rare (Humans): Eye hemorrhage, anemia, leukopenia, thrombocytopenia, pancytopenia, QT prolongation, nephrotoxicity
Cautions & contraindications
- Hypersensitivity to voriconazole or other azole antifungals
- Concurrent use with barbiturates, carbamazepine, cisapride, pimozide, quinidine, rifampin, or rifabutin
- Caution in patients with hepatic dysfunction
- Caution in patients with proarrhythmic conditions
- Caution with the IV formulation in patients with decreased renal function (due to accumulation of the SBECD vehicle)
- > **Feline Warning**: Cats are highly susceptible to severe neurologic and systemic adverse effects. Use only as a last resort. * **Hepatic Effects**: Can cause liver enlargement and enzyme induction (in dogs). Use with caution in patients with pre-existing hepatic dysfunction. * **Renal Impairment**: The IV formulation contains sulfobutyl ether beta-cyclodextrin sodium (SBECD), which can accumulate in patients with reduced renal function. * **Pregnancy**: Teratogenic in rats and embryotoxic in rabbits (FDA Category D). Weigh risks vs. benefits in pregnant animals. * **Cardiac**: Use with caution in patients with proarrhythmic conditions.
Drug interactions
- Antidiabetic agents (sulfonylureas): May increase serum concentrations of these drugs and increase risk for hypoglycemia
- Barbiturates (phenobarbital): Decreased voriconazole concentrations; concurrent use is contraindicated
- Benzodiazepines: May increase benzodiazepine concentrations
- Calcium-channel blockers (amlodipine, diltiazem, verapamil): May increase serum concentrations; dosage adjustment may be required
- Carbamazepine: Decreased voriconazole concentrations; concurrent use is contraindicated
- Cisapride: Potential for serious cardiac arrhythmias; concurrent use is contraindicated
- Corticosteroids (prednisolone): Potentially increased AUC for prednisolone
- Immunosuppressive agents (cyclosporine, tacrolimus): Increased concentrations; decrease cyclosporine dosage by 50% and tacrolimus dosage by 33% when starting voriconazole
- Methadone: May increase plasma concentrations of R-methadone; monitor for toxicity
- Phenytoin: Can decrease voriconazole concentrations and voriconazole can increase phenytoin concentrations
Frequently asked questions
What is Voriconazole used for in pets?
**Voriconazole** is an advanced antifungal medication used for severe or resistant fungal infections. * **Investigational Use**: This drug is relatively new in veterinary medicine, and its use is often considered investigational. It is also quite expensive. * **Administration**: Give the medication at least one hour before or one hour after feeding to ensure proper absorption. * **Adverse Effects to Watch For**: Because experience with this drug in pets is limited, monitor your pet closely. **Contact your veterinarian immediately** if you notice: * Itching or skin rashes * Yellowing of the whites of the eyes or gums (jaundice) * Reduced appetite or weight loss * Difficulty walking, stumbling, or weakness (especially in the hind legs) * Vision problems or dilated pupils * **Cats**: Cats are particularly sensitive to this medication. Watch them extremely closely for any changes in behavior, appetite, or mobility.
Is Voriconazole safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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