Chemotherapy Drug Poisoning in Dogs and Cats

Chemotherapy drugs are used to treat cancer and other conditions in people because they target and kill rapidly dividing neoplastic (cancer) cells and other cells. They’re primarily used as anti-cancer agents, but may also provide benefit for a variety of auto-immune disorders and for organ transplant recipients as immunosuppressive agents.

medicationsChemotherapy medications are derived (semi)synthetically or from plants, and are prescribed in intravenous (IV), oral, and topical forms.

How safe are chemotherapy drugs if exposed to dogs and cats?

With pets, there may be a narrow range of safety with certain chemotherapy drugs.

"Caution! Significant or even life-threatening symptoms may occur if your pet ingests certain chemotherapy drugs. Call your veterinarian or Pet Poison Helpline* (800-213-6680) immediately if this happens!"

  • Some of the medications, such as prednisone or cyclosporine, have a wide margin of safety — although if you know your dog or cat ingests them, you should always call your veterinarian or Pet Poison Helpline* (800-213-6680) for guidance.
  • Other drugs, such as 5-fluorouracil (5-FU) or methotrexate, can cause serious problems, even at low dose. For instance, 5-FU is highly toxic to pets when ingested orally as a topical medication.
  • Caution! Significant or even life-threatening symptoms may occur if your pet ingests such pills or chew on tubes of topical preparations. Call your veterinarian or Pet Poison Helpline* (800-213-6680) immediately if this happens!

Why are chemotherapy drugs poisonous for dogs and cats?

The intent of these medications is to reduce the production of or kill rapidly dividing cells. Therefore, if a pet ingests a chemotherapy drug, dangerous health threats may develop, including:

  • Lethargy,
  • Depression,
  • Drooling secondary to nausea,
  • Inappetance (lack of appetite,
  • Vomiting,
  • Diarrhea (with or without blood),
  • Abdominal pain,
  • Suppressed immune system (e.g., low white blood cells),
  • Anemia,
  • Reduced number of platelets (called a thrombocytopenia),
  • Liver damage,
  • Acute kidney failure,
  • Ataxia (lack of muscle coordination)
  • Disorientation,
  • Severe and non-responsive seizures,
  • Blindness, and
  • Death.

When patients die from ingesting chemotherapy drugs, it’s usually due to secondary complications caused by the immunosuppression from the chemotherapy drug. Sepsis, which is when bacteria enters the bloodstream, or severe bleeding into the brain or spinal column (from severe thrombocytopenia) can rarely occur, resulting in potential death.

What amount of chemotherapy drug exposure is poisonous to a dog or cat?

It all depends on the chemotherapeutic medication type, dose, and if it’s a dog or cat.

  • Some topical preparations can cause fatal effects when a cat or dog chews on a small, one-ounce tube.
  • Symptoms have also been reported from dogs and cats chewing on the IV fluid line while the owner receives treatment at home.
  • Other medications only cause symptoms when used chronically, and are of little concern in the one-time or accidental situation.

"Some topical preparations can cause fatal effects when a cat or dog chews on a small, one-ounce tube."

What should I do if my dog or cat eats a chemotherapy drug?

istock_000009204979mediumIf you suspect or know that your pet has eaten a tablet or punctured a tube of a chemotherapy drug, please contact your veterinarian or Pet Poison Helpline* (800-213-6680) immediately. The sooner you seek treatment, the better the prognosis and outcome for your pet!

CAUTION: Do not induce vomiting or give anything orally to your dog or cat unless your veterinarian or Pet Poison Helpline* specifically directs you to do so. Since some pets may develop central nervous system signs rapidly, inducing vomiting can make them worse!

With any drug exposure, you should get treatment for your pet as quickly as possible.

What are the symptoms of chemotherapeutic poisoning in a dog or cat?

Symptoms can either develop within 30 minutes of consumption or take hours to days to occur. These may include any or all of the following:

  • Drooling
  • Lethargy or depression
  • Anorexia or inappetance
  • Vomiting
  • Diarrhea
  • Incoordination or difficulty walking or standing (walking like drunk)
  • Tremors
  • Seizures
  • Weakness
  • Bruising
  • Bloody urine

How does my veterinarian diagnose chemotherapy poisoning in dogs and cats?

Your veterinarian makes a presumptive diagnosis if you know or suspect that your pet swallowed or chewed on a chemotherapeutic or immune modulating product, and your veterinarian identifies symptoms of gastrointestinal upset or central nervous system problems. Not all medications cause immediately visible symptoms. Your veterinarian may want to run baseline blood work to know what’s normal for your pet, since the bone marrow suppression may take days to develop. Bone marrow suppression may have long-lasting effects, up to weeks out, and follow up complete blood count tests may be necessary.

Is there an antidote for chemotherapy toxicity in dogs and cats?

While there’s no direct antidote for chemotherapy toxicity, there are some types of medication that can help stimulate the bone marrow, increasing the white blood cell count or red blood cell count.

How are pets treated for chemotherapy drug ingestion?

Your veterinarian will need to provide fast and aggressive treatment to effectively reverse any poisonous effects and prevent the development of severe problems. If you know your pet ingested drugs but is not showing signs, treatment recommendations may include:

  • Decontamination (including inducing vomiting and administering charcoal to bind up the drug from the stomach and intestines)
  • Blood work monitoring
  • Supportive care.

If your dog or cat shows signs of illness or distress, your veterinarian will prescribe treatment based on your pet’s condition. In addition to the baseline blood work we mentioned, your pet will need to be hospitalized so your pet can be monitored and given intravenous fluids, anti-vomiting medication, anti-seizure medication, and any other supportive care that’s needed. Your veterinarian will need to repeat some blood work to monitor for symptom development. In the case of significant bone marrow suppression, your pet may require a blood transfusion.

Can a pet recover from chemotherapy drug poisoning?

It depends on which chemotherapy drug was ingested, how much was ingested, and how quickly treatment was started. As symptoms occur over time without treatment, the prognosis drastically decreases and can be very grave.

How can I prevent chemotherapy poisoning in my pet?

If you personally use chemotherapeutic agents, please keep them stored in a safe place at all times, out of reach of your pets. In addition, please keep your pet(s) from licking topical ointment on your body and keep them away from any IV administration kits.

"If you personally use chemotherapeutic agents, please keep them stored in a safe place at all times, out of reach of your pets."

IMPORTANT! With any poisoning in pets, call your veterinarian or Pet Poison Helpline for prompt decontamination and treatment. Early treatment is less dangerous to your pet, and less expensive for you!

pet_poision_helpline_logo*Pet Poison Helpline, is an animal poison control service available 24 hours, 7 days a week for pet owners and veterinary professionals who require assistance treating a potentially poisoned pet. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at www.petpoisonhelpline.com. Pet Poison Helpline is not directly affiliated with LifeLearn.

This client information sheet is based on material written by: Dr. Heather Handley, Staff Veterinarian, Pet Poison Helpline

© Copyright 2012 LifeLearn Inc. Used and/or modified with permission under license.

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