Fomepizole

Major Uses

Fomepizole is a synthetic alcohol dehydrogenase inhibitor used to treat ethylene glycol poisoning in dogs and cats.

Common Precautions

Because fomepizole is given in injection form, it should be very carefully diluted, commonly with sodium chloride, before administration. If this drug is administered concurrently with other competitive medications, it can cause central nervous system depression and respiratory difficulties in the patient. Injection may cause vein irritation and phlebosclerosis. Some trials reported anaphylaxis developing in dogs, which can be observed by symptoms such as gagging, excessive salivation, tachypnea, and trembling. Cats may suffer from mild sedation when using Fomepizole.

Fomepizole should not be used in animals with a known allergy or hypersensitivity to the drug. A veterinarian should be contacted immediately if an overdose is suspected, the symptom of which is most commonly additional central nervous system depression.

Storage

Fomepizole should be kept at room temperature, as the injection is prone to solidifying when kept at a temperature of less than 77 degrees Fahrenheit. Should solidification occur, warm running water should be used until it is liquid again. If it is re-solubilized, the vial should be disposed of after 72 hours if not used.

Administration

Fomepizole is administered as an injection. The initial injection in dogs should be 20 mg/kg, and then another injection of 15 mg/kg should be administered at 12 and 24 hours after the initial injection. A dose of 5mg/kg should be administered at 36 hours, followed by additional 5mg/kg doses every 12 hours if the animal has not recovered by this point. For cats, the initial dose should be 125 mg/kg with additional doses of 31.25 mg/kg at 12, 24, and 36 hours.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.