Atlantic Veterinary Internal Medicine & Oncology (AVIMO)
Chemotherapeutic Drugs
Chemotherapy is an important tool in treating cancer in both dogs and cats, and our goal is always to improve quality of life while managing the disease. Unlike in people, pets generally tolerate chemotherapy well, with most experiencing only mild side effects—if any. Quality of life is the forefront of cancer treatment in pets.
Every treatment plan is tailored to your pet’s specific diagnosis, overall health, and lifestyle. We’ll guide you through the benefits and risks of each option and help you understand what to expect throughout the process. If your pet experiences any side effects—such as vomiting, diarrhea, lethargy, or changes in appetite—please contact your pet’s oncologist. Many side effects can be managed with supportive care or simple adjustments to the treatment plan. In rare cases, we may pause or change the medication to ensure your pet stays comfortable and safe
Chemotherapy can be given in a few different ways, most commonly as an injection at the hospital or as oral medication administered at home. Oral chemotherapy can be a convenient option for some pets and families, while injectable treatments are often administered on a regular schedule at our clinic under close supervision.
Our team is here to support you every step of the way, answering questions and helping you feel confident in the care your pet receives. We know your pet is family, and we’re committed to treating them with the compassion and respect they deserve.
When Do We Choose Chemotherapy?
Chemotherapy is one of several tools we use to treat cancer in pets, and whether or not it’s recommended depends on the type of cancer, how far it has progressed, and your pet’s individual needs. In some cases, chemotherapy is the primary treatment, while in others, it works best in combination with surgery or radiation therapy. There are also situations where chemotherapy is the only viable option when other treatments aren't possible.
We always take a thoughtful, case-by-case approach to ensure your pet receives care that aligns with your goals and prioritizes quality of life.
Chemotherapy may be recommended in the following situations:
When treating cancers that are known to respond well to chemotherapy, such as lymphoma
When cancer is present in multiple areas of the body (multicentric disease)
When cancer has already spread to other parts of the body (metastatic disease)
When the tumor cannot be surgically removed (non-resectable disease)
As a follow-up to surgery or radiation for cancers that are likely to spread over time
When surgery was performed, but the tumor could not be completely removed, or microscopic cancer cells may remain
If chemotherapy is part of your pet’s treatment plan, we’ll take the time to explain how it works, what to expect, and how we’ll help manage any potential side effects. Our goal is always to help your pet live as comfortably and happily as possible while providing the best chance for a positive outcome.
Chemotherapy Side Effects:
If chemotherapy is part of your pet’s treatment plan, you may naturally have questions and concerns—particularly about possible side effects. Fortunately, chemotherapy in veterinary medicine is generally well-tolerated, and our approach is always focused on maintaining your pet’s quality of life.
Compared to humans undergoing chemotherapy, dogs and cats tend to experience fewer and milder side effects. This is because we use lower doses of medication and typically avoid combining multiple chemotherapy drugs unless absolutely necessary. As a result, fewer than 10% of pets experience significant side effects, and most patients experience little to no discomfort during treatment.
The most common side effects in pets are gastrointestinal in nature. These may include mild vomiting, diarrhea, or a temporary decrease in appetite. These symptoms typically occur within one to three days after treatment and often resolve on their own or with the help of simple medications. In some cases, we may recommend anti-nausea or anti-diarrheal drugs, or a short-term switch to a bland diet. Severe gastrointestinal upset is rare but may require hospitalization and fluid therapy, if it occurs. We’ll give you detailed instructions specific to your pet’s medications so you’ll know what to watch for and when to call us.
Another possible side effect is bone marrow suppression. Many chemotherapy drugs can affect rapidly dividing cells, including those in the bone marrow, which are responsible for producing white blood cells. A temporary drop in white blood cell count may occur seven to fourteen days after treatment, depending on the drug used. We monitor your pet’s bloodwork closely with regular complete blood counts (CBCs). If your pet’s white cell count becomes low, we may prescribe prophylactic antibiotics to reduce the risk of infection. Pets that develop signs of illness—such as fever, weakness, or lethargy—may require hospitalization and intravenous fluids and antibiotics for a short period. Fortunately, most pets recover fully within a few days with appropriate supportive care.
Unlike people, most pets do not experience significant hair loss during chemotherapy. Hair growth patterns in animals are different, and shedding is not typically affected. However, some dogs and cats may lose their whiskers, and hair regrowth in areas that have been shaved may be slower during treatment. Certain dog breeds with continuously growing hair coats, such as poodles or bichon frisés, may experience noticeable thinning or patchy hair loss, but hair usually begins to grow back once treatment ends.
If your pet does experience moderate or severe side effects, we will adjust the treatment plan accordingly. This may involve lowering the dosage, changing medications, skipping a treatment, or discontinuing chemotherapy altogether depending on how your pet responds. Our goal is always to treat the cancer while keeping your pet as comfortable and happy as possible.
At the heart of everything we do is a commitment to your pet’s comfort and well-being. While the idea of chemotherapy can be daunting, it’s reassuring to know that most pets respond positively to treatment and can continue to enjoy a good quality of life. We’re here to answer your questions, monitor your pet closely, and ensure you feel confident and supported throughout the treatment journey.
What to Expect During Chemotherapy Visits
The way chemotherapy is given—and how long treatment continues—can vary depending on your pet’s specific type of cancer, the medications being used, and how your pet is responding to therapy. Every treatment plan is carefully tailored to meet the individual needs of each patient.
Most chemotherapy appointments are scheduled as outpatient visits and are part of a regular recheck. During these visits, your pet may stay with us for a few hours while we perform routine monitoring, which may include bloodwork and imaging. These tests help us ensure your pet is healthy enough to safely receive treatment that day.
Once your oncologist has reviewed the results and completed an exam, and if all looks well, your pet will receive their chemotherapy from our experienced and compassionate technical team. After treatment, your pet will be able to return home the same day to rest and recover in the comfort of familiar surroundings.
Our goal is to make each visit as smooth and stress-free as possible—for both you and your pet. If you ever have questions about the process, we're always here to help.
How Are Chemotherapy Drugs Given?
Chemotherapy can be administered in a few different ways:
Oral medications: Some chemotherapy drugs come in pill or capsule form that you can give at home. Your veterinarian will provide detailed instructions for safe handling and administration.
Injections: Many chemotherapy agents are given as brief injections under the skin (subcutaneous) or into a vein (intravenous). These are typically performed during an outpatient visit.
Intravenous infusions: A few chemotherapy drugs require a slow infusion over several hours—typically between 4 to 8 hours. These treatments are done in the hospital and may require your pet to stay with us for the day.
How Often Are Treatments Given?
The frequency of chemotherapy depends on the protocol you and your veterinary oncologist has selected. Treatment schedules may include:
Weekly treatments (common during initial phases of therapy)
Every-other-week or monthly treatments (common in maintenance or low-dose protocols)
Pulse treatments (short bursts of treatment followed by rest periods)
Your doctor will tailor the schedule to your pet’s needs, the type of cancer, and how well your pet is tolerating treatment. We always aim to minimize stress while maximizing comfort and effectiveness.
How Long Does Treatment Last?
The length of chemotherapy treatment depends on the type and stage of cancer and how well your pet responds. Here are a few general guidelines:
Some pets may receive chemotherapy for a fixed period, such as 4–6 months, especially if they go into remission (meaning no detectable cancer is present).
Others may continue on maintenance chemotherapy for longer periods, if the cancer remains stable and your pet is tolerating the treatment well.
If a cancer recurs (returns), chemotherapy can often be resumed or adjusted to regain control.
Ongoing Monitoring
Throughout chemotherapy, we will monitor your pet’s progress closely through:
Regular physical exams
Bloodwork to evaluate organ function and white blood cell counts
Imaging or measurements of tumors or lymph nodes (if applicable)
Adjustments to your pet’s treatment plan will be made based on how they are responding and how well they are tolerating the medications.
Our Goal
We know this process can feel overwhelming at times, but our goal is to ensure that your pet’s treatment is as safe, effective, and comfortable as possible. Whether treatment lasts for weeks, months, or longer, we are here to guide you every step of the way and help you make informed, compassionate decisions that prioritize your pet’s well-being.
Handling Chemotherapy
To help keep your household safe while your pet is receiving chemotherapy, please follow these precautions:
Medication Handling
Always wear gloves when handling chemotherapy medications. Wash hands thoroughly afterward.
Tablets and capsules must be given whole—do not split, crush, or open.
Most medications can be given with food. Use a small food portion to ensure your pet gets the full dose before offering the rest of the meal.
Medications should not be handled by children, pregnant or nursing women, or immunocompromised individuals.
Store all medications in their original containers, out of reach of children and pets.
Contact us for proper disposal of any unused medication—do not throw away or flush.
After Treatment Care
Chemotherapy may be present in your pet’s urine and feces for 72 hours after treatment.
Wear gloves and wash hands after cleanup.
Prevent your pet from eliminating in areas where children play.
If bedding is soiled, wash it separately in hot water using gloves.
If your pet vomits within 12 hours of taking an oral chemo dose, wear gloves when cleaning up and wash hands afterward.
If you have any questions or concerns, please don’t hesitate to call us!
Prognosis in Pets Receiving Chemotherapy
When your pet is diagnosed with cancer, one of the first questions you may have is, “How much time do we have?” While we understand how important this question is, the answer is often complex.
Based on both the veterinary literature and our many years of clinical experience in oncology, we can often provide an estimated prognosis or life expectancy—both with and without treatment. These estimates vary depending on the type and stage of cancer, your pet’s overall health, how the disease is behaving, and how it responds to therapy.
However, it's important to understand that every pet is unique, and cancer can behave unpredictably. In some cases, prognosis data is limited or unclear, especially for rare types of cancer. Even within the same type of cancer, individual responses to treatment can vary significantly, which can make outcomes difficult to predict with certainty.
While most cancers in pets are not curable, many can be managed successfully for extended periods through chemotherapy or other treatments. In these cases, our goal is palliative care—to slow down the progression of disease, relieve symptoms, and maintain or improve your pet’s quality of life. In some cases, pets live many months or even years longer than expected, with a good quality of life throughout that time.
Regardless of the treatment path you choose—whether it’s aggressive therapy, palliative support, or a focus on comfort—we will always prioritize your pet’s quality of life. Every recommendation we make is based on the balance between extending your pet’s time with you and ensuring that time is comfortable, meaningful, and full of the things they enjoy most.
We are committed to walking this path with you, offering guidance, compassion, and the best possible care for your pet at every stage of their journey.
