What are the risks or side effects involved with chemotherapy?

There are risks and side effects involved with any type of chemotherapy treatment, although we administer medications at the time of treatment and also dispense medication for you to use at home to minimize these side effects. For any one treatment about half of our veterinary patients will not have any noticeable side effects. If side effects do occur, they are often self-limiting or manageable with medication. A minority of patients develop serious, life threatening side effects. If side effects are affecting your pet’s quality of life, we will often change drugs, so please let us know if you have any concerns.

The most common side effects are mild vomiting, diarrhea, and loss of appetite; these are due to the effect of chemotherapy on rapidly dividing stomach and intestinal cells. These signs usually occur 1-7 days after treatment, are usually mild and can be treated with supportive care at home. In some instances more serious side effects can occur requiring hospitalization with intravenous fluids, nutritional support and antibiotics. Fortunately, severe reactions are uncommon.

Low white blood cell counts commonly occur 7-14 days after chemotherapy treatment. This is caused by the effect of chemotherapy on the rapidly dividing bone marrow cells that produce white and red blood cells. If your pet’s white blood cell count is low, we will delay scheduled chemotherapy until the count is normal. We may start antibiotics and other medications to protect your pet against infection while the count is low. The white blood cell count recovers without treatment in a few days in the vast majority of patients.
Hair loss is not common in veterinary patients receiving chemotherapy although shaved areas can take a long time to regrow during chemotherapy. Certain breeds that will experience hair loss during chemotherapy include Poodles, Old English Sheepdogs, Schnauzers, Pulis, Lhasa Apsos, Shih Tzus, Malteses and any dog that needs regular hair clipping. If hair loss does occur, it usually occurs in the initial phases of chemotherapy, and the hair will eventually grow back once the treatments are spread out. The hair that grows back is often softer and finer. Cats do not generally lose hair but may lose their whiskers.
After each treatment you will receive a handout with information regarding the drug administered that day, expected side effects and recommendations.

Will my pet be sick the day of treatment?

Immediate reactions to chemotherapy are rare and occur shortly after treatment; we monitor patients carefully after treatment for these reactions prior to sending them home. In general, chemotherapy patients do not feel ill the day of therapy and should be able to participate in all normal activities on the day of treatment. We want your pet to have a great quality of life during therapy and enjoy all of their favorite activities as much as possible.

How is chemotherapy given?

Many chemotherapy drugs are given intravenously through an IV catheter; others are administered as injections under the skin or orally. Prior to administration of chemotherapy, we examine every patient, do bloodwork to check white blood cell counts and other parameters, calculate drug dosages, prepare the drugs for administration and often administer anti-nausea medications and other medications to help prevent side effects. Once all of these steps are completed, we administer the chemotherapy drugs to your pet. After administration, your pet is observed for any reactions to the drugs prior to going home.

Is my pet sedated for chemotherapy?

In general pets are not sedated for chemotherapy. If sedation is needed, you will be contacted before treatment.

Is chemotherapy painful?

Chemotherapy is often an IV injection and is not painful; once we place our IV catheter, the drug is administered just like other intravenous medications or fluids. The injectable forms of chemotherapy given under the skin are similar in sensation to a vaccine. The oral forms are given with food in the hospital or at home.

How long is my pet going to receive chemotherapy?

The length of treatment will depend upon the type of cancer being treated. We will give you a protocol or chemotherapy treatment plan at your first consultation.

Can I be with my pet during the administration of chemotherapy?

In most cases the treatment is quick, and your pet will only be away from you for a small amount of time. It is safer if you are not present due to the small risk to you of chemotherapy exposure. Most patients handle their treatments very well.

What happens if my pet has an emergency?

In the unusual case that your pet needs immediate medical attention, you should come directly to either the Pet Emergency & Specialty Center of Marin or go to your local veterinarian. Dr. Sabhlok is happy to speak with the attending veterinarian to consult about the case if possible.

Should family members or other pets be separated from my pet receiving chemotherapy?

Most chemotherapy drugs and their metabolites clear the patients system within 24-48 hours of treatment. We recommend that for the first 48 hours after therapy that your pet eliminate away from flowerbeds or children’s play areas. If an accident occurs in the house (urine, feces, vomit), simply use disposable rubber gloves to clean up all fluids, place in a plastic bag and place bag in the trash. Normal activities with your pet such as petting, playing, sleeping in bed and grooming are considered safe during chemotherapy. Children, especially infants and toddlers (due to their tendencies to put their hands in their mouths) should not handle body fluids from pets receiving chemotherapy.

Will my pet’s cancer be cured?

Similar to the treatment of human cancers, most cancers are not cured but rather controlled as a chronic disease. Our focus in veterinary oncology is on quality of life. Although most pets with cancer eventually have a recurrence and may succumb to their illness in the future, the time that they are on chemotherapy is usually of excellent quality. We can provide many months or sometimes years of happy life to most veterinary patients. If your pet experiences any effects from therapy that affect their quality of life, please let us know so we can adjust our therapy.

Helpful Link:

Veterinary Cancer Society

Welcome to the Oncology Service. Our primary goal is to increase your pet’s quality of life throughout therapy. Below are some frequently asked questions, but please feel free to speak with us further - we are here for you!


What is chemotherapy?

Chemotherapy is the treatment of cancerous illness with chemical compounds. Chemotherapy drugs are compounds that are toxic to cancer cells and can be given intravenously, intramuscularly, subcutaneously, or orally.

How does chemotherapy work?

Chemotherapy agents kill rapidly dividing cells; many of these cells are rapidly dividing cancer cells. Chemotherapy interferes with the cells’ ability to divide through many different mechanisms and this eventually kills the cells.