Fomepizole
Also known as: Antizol, Antizol-Vet
> **Medical Emergency**: Antifreeze (ethylene glycol) poisoning is a life-threatening emergency. Time is absolutely critical. * **Rapid Action Needed**: Dogs treated within 8 hours of ingestion have a much better chance of survival. Cats are extremely sensitive and must be treated within **3 hours** of ingestion. * **Intensive Care**: Treatment requires hospitalization in an intensive care setting. Your pet will need IV fluids, frequent blood tests, and close monitoring. * **Cost**: The antidote (fomepizole) and the associated intensive care can be quite expensive, especially for large dogs. You will need to make an informed decision rapidly to give your pet the best chance of survival.
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
- For treatment of ethylene glycol toxicity
- For treatment of ethylene glycol toxicity
How it is given
Possible side effects
- Vein irritation and phlebosclerosis (if given rapidly or undiluted)
- Anaphylaxis (rare)
- Mild sedation (particularly in cats)
Cautions & contraindications
- No labeled contraindications, but use with caution if the patient is already receiving ethanol therapy.
- > **Dilution Required**: Concentrated drug must be diluted as directed before intravenous administration to prevent severe vein irritation. * **Timing**: Efficacy drops significantly if given after 8 hours in dogs, or after 3 hours in cats. If azotemia is present, prognosis is poor. * **Supportive Care**: Fomepizole must be used alongside aggressive fluid therapy and correction of acid-base/electrolyte imbalances. * **Decontamination**: If the patient presents within 1-2 hours of ingestion, consider inducing emesis or performing gastric lavage with activated charcoal to minimize absorption. * **Pregnancy**: FDA Category C. Benefits generally outweigh risks in life-threatening toxicity.
Drug interactions
- Ethanol: Fomepizole inhibits alcohol dehydrogenase; ethanol metabolism is reduced significantly and alcohol poisoning (CNS depression, coma, death) can occur. Concurrent use is generally not recommended. If used together, mandatory monitoring of ethanol blood levels is required.
Frequently asked questions
What is Fomepizole used for in pets?
> **Medical Emergency**: Antifreeze (ethylene glycol) poisoning is a life-threatening emergency. Time is absolutely critical. * **Rapid Action Needed**: Dogs treated within 8 hours of ingestion have a much better chance of survival. Cats are extremely sensitive and must be treated within **3 hours** of ingestion. * **Intensive Care**: Treatment requires hospitalization in an intensive care setting. Your pet will need IV fluids, frequent blood tests, and close monitoring. * **Cost**: The antidote (fomepizole) and the associated intensive care can be quite expensive, especially for large dogs. You will need to make an informed decision rapidly to give your pet the best chance of survival.
Is Fomepizole 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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