This document summarizes the anticancer drugs used for cancer treatment in dogs and cats.
Some might have been informed that dogs and cats experience fewer side effects, but is this really true?
Pets cannot verbalize feelings such as nausea, lethargy, or loss of appetite. It’s crucial for pet owners to understand and interpret their dogs’ and cats’ feelings accordingly.
There are no anticancer drugs exclusively for animals available.
Therefore, anticancer drugs meant for humans are used in the treatment of animals.
When using anticancer drugs for dogs and cats, some veterinarians might explain that “dogs and cats are less likely to experience side effects” or that “there are no side effects,” but there is no such thing as an anticancer drug with no side effects.
Unlike humans, dogs and cats cannot express feelings like “I feel a bit sick,” “I want to vomit,” “I have a headache,” or “My limbs are numb.”
However, have you noticed a decrease in appetite or an increase in the time they spend lying down after your dog or cat receives chemotherapy?
Additionally, blood tests might reveal abnormalities in the liver, kidneys, white blood cells, or platelets.
These are almost certainly side effects of the anticancer drugs.
It is impossible to separate the side effects from the use of anticancer drugs.
If your dog or cat is diagnosed with cancer, do not start chemotherapy immediately. Thoroughly understand the potential benefits and drawbacks, the expected effectiveness, and the risks of side effects.
We recommend that you carefully and calmly evaluate whether the treatment would be beneficial for your beloved dog or cat.
Anticancer drugs are highly specialized medications.
Their characteristics are clearly different from other pharmaceutical products.
They are used only after a confirmed diagnosis of cancer, not just a suspicion. They are also not used for prevention.
Characteristics of Anticancer Drugs
Used only after a confirmed diagnosis of cancer, not for suspected cancer.
Never used for prevention.
If used on healthy animals, there is a risk of inducing cancer.
Designed to attack cancer cells, but can also affect normal cells.
The mechanisms by which cancer is attacked involve inhibiting cancer cell proliferation and causing cell division to fail.
Side effects occur frequently, ranging from mild to life-threatening.
Bone marrow suppression is a common side effect, making it easy for white blood cell and platelet counts to decrease.
The immune system becomes weakened, making it easier to contract infections.
Nausea and diarrhea, among other gastrointestinal issues, are common.
Liver function tends to deteriorate.
Except for certain types of cancer, chemotherapy alone rarely leads to a complete cure.
While initial use may show efficacy, repeated use often leads to resistance, reducing effectiveness.
There are immediate side effects and those that manifest with prolonged use.
The dosage is set based on what the body can tolerate, rather than what completely eradicates the cancer.
To enhance effectiveness, chemotherapy drugs with different mechanisms are often used in combination.
Additionally, in recent years, the use of “targeted cancer therapies,” known to have lighter side effects than traditional chemotherapy, has been increasing.
List of Common Chemotherapy Drugs
Here is a summary of common chemotherapy drugs used in animal chemotherapy. These are all drugs for humans.
There are no chemotherapy drugs specifically approved for animals, so all chemotherapy used for dogs and cats comes from human medications.
*Although the active ingredients are the same, the brand names may differ between human and veterinary drugs.
Briplatin / Land Cisplatin
These are platinum-based chemotherapy drugs containing a platinum atom.
They bind to DNA in cells, forming crosslinks, which strongly inhibit cell proliferation.
Due to their very compact molecular size, they are believed to easily reach cancer tissues.
While they possess strong anticancer effects, severe side effects do occur. Nausea and kidney dysfunction need to be carefully managed.
Symptoms to Monitor
Decreased urine output
Swelling
Itching
Swelling around the eyes or mouth
Rapid breathing
Vomiting
Decreased appetite
Unsteadiness
It is sometimes used for melanomas in dogs and cats.
Paraplatin – Carboplatin
This is also a platinum-based drug, like cisplatin.
Carboplatin is an improved version of cisplatin and has significantly reduced nephrotoxicity compared to cisplatin, but this trade-off comes with a reduction in anticancer efficacy.
Symptoms to Check
Vomiting or loss of appetite
Hair loss
Lethargy
Diarrhea
Blood in urine
Signs of distress
Weight loss
Dogs and cats may be treated for melanoma using this medication.
Taxol — Paclitaxel
It binds to structures in the cell called microtubules. Microtubules are involved in cell division; when Taxol binds to them, the cells cannot divide or multiply.
There is a risk of severe allergic reactions when administered, so steroids and antihistamines are given beforehand. In humans, nearly 100% of patients experience hair loss.
Symptoms to Check
Vomiting or loss of appetite
Hair loss
Changes in preferred foods (taste disorder)
Lethargy (fatigue)
Diarrhea or constipation
Signs of distress
Endoxan — Cyclophosphamide
An older medication with a long history, it is still used for malignant lymphoma.
It binds to DNA, inhibiting cell division and growth, and precautions should be taken for infections due to bone marrow suppression. There can be occurrences of hemorrhagic cystitis.
Symptoms to Check
Vomiting or loss of appetite
Hair loss
Lethargy
Blood in urine
Frequent urination
Adriamycin — Doxorubicin
It possesses strong anticancer properties.
Used for malignant lymphoma, it inhibits the enzymes necessary for DNA replication. A possible side effect is heart damage.
## Symptoms to Check
Is there any vomiting or loss of appetite?
Is there any hair loss?
Does your pet seem lethargic?
Is there blood in the urine?
Is there increased urination frequency?
(Cats) Renal Toxicity ※ Doxorubicin should be used with caution as it can cause severe toxicity in Collies, Shetland Sheepdogs (Shelties), and cats.
Oncovin – Vincristine
This drug inhibits the functions of organelles called microtubules within cells.
By its action, it suppresses cell division and proliferation. It is used for malignant lymphoma and leukemia.
It is prone to cause nerve damage, which may result in numbness of the fingers or difficulty in walking.
## Symptoms to Check
Is there any hair loss?
Does your pet seem lethargic?
Is there any difficulty urinating?
Are there any issues with walking?
In cats with renal impairment, mitoxantrone is used as an alternative to doxorubicin.
L-Asparaginase
Product Name: Elspar
This medication is administered subcutaneously. (Some experts recommend intramuscular administration)
This anti-cancer drug works by breaking down asparagine (a type of amino acid) needed for tumor cell proliferation, causing nutritional deficiency and resulting in cell death.
While this medication has relatively few side effects, repeated administration can lead to anaphylaxis, so caution is necessary.
(As a preventive measure, antihistamines might be administered 15-30 minutes before the medication)
It can be effective even when used alone, but because tumor cells can develop resistance to L-asparaginase very quickly, subsequent treatment is crucial.
Side effects include anaphylactic reactions.
CCNU
Product Name: Lomustine
This medication is administered orally.
It is an anti-cancer drug that suppresses tumor cell growth by inhibiting DNA synthesis and is used for lymphomas, mast cell tumors, histiocytic diseases, and brain tumors since it can cross the blood-brain barrier.
Side effects include gastrointestinal toxicity, bone marrow toxicity, and liver failure with continued therapy.
Methotrexate
Product Name: Methotrexate
This medication is administered orally or intravenously. It is a folic acid metabolism antagonist that inhibits the action of enzymes that aid in DNA and RNA synthesis within cells, thereby suppressing the growth of cancer cells.
Side effects include bone marrow toxicity and damage to intestinal epithelium.
Actinomycin
Trade names: Cosmegen, Dactinomycin
This medication is administered intravenously. It binds to DNA and inhibits RNA synthesis, preventing the growth of cancer cells, and has a tendency to remain within tumor cells.
If it leaks out around the blood vessels, it can cause severe skin necrosis.
Side effects include gastrointestinal toxicity and bone marrow toxicity.
Chlorambucil *Not approved in Japan
Trade names: CeeNU, Leukeran, Lecukeran
This medication is administered orally. It is a chemotherapeutic agent that inhibits DNA synthesis and reduces the growth of tumor cells. It can be used when sterile hemorrhagic cystitis caused by cyclophosphamide occurs or is likely to occur.
Side effects include gastrointestinal toxicity, bone marrow toxicity, and neurological symptoms.
Melphalan
Trade name: Alkeran
This medication is administered orally. It is a chemotherapeutic agent that inhibits DNA synthesis and reduces the growth of tumor cells. It can be used in combination with prednisolone (MP therapy) for plasmacytoma.
Side effects include gastrointestinal toxicity, bone marrow toxicity, and liver toxicity.
Cytarabine
Trade name: Cytosar
This medication is administered subcutaneously, intravenously, or intrathecally. It is one of the most commonly used chemotherapeutic agents in the United States. It is converted within cells to cytarabine triphosphate, a pyrimidine analog, which inhibits DNA synthesis and reduces the growth of tumor cells.
It can cross the blood-brain barrier and is also used for brain tumors.
Side effects include gastrointestinal toxicity, bone marrow toxicity, liver toxicity, and cytarabine syndrome (fever, muscle pain, bone pain, conjunctivitis, maculopapular rash, etc.).
Prednisone – Prednisolone
Prednisone (Prednisolone) is not a chemotherapeutic agent but a synthetic adrenal corticosteroid (steroid).
It is primarily used as a medication to suppress allergies and inflammation. Although not a chemotherapeutic agent, it is used in the treatment of malignant lymphoma. Due to its immunosuppressive effects, it increases susceptibility to infections.
Additionally, its side effect of stimulating appetite can be utilized to encourage eating in patients with decreased appetite.
The combination therapy using cyclophosphamide, doxorubicin, vincristine, and prednisone is called CHOP therapy, which is a representative regimen (combination of chemotherapeutic agents) for malignant lymphoma. Malignant lymphoma is relatively responsive to chemotherapeutic agents.
However, unfortunately, due to the issue of drug resistance, it is rare for malignant lymphoma to be cured solely by chemotherapeutic agents.
If pets undergo chemotherapy, side effects are almost inevitable.
Even if the cancer shrinks, if the pet becomes lethargic due to side effects, it can’t be said that the quality of life is being maintained.
It is expected that immunological measures can lighten side effects and accelerate recovery.
Moreover, there is a risk of liver function decline during chemotherapy, so combining Cordy, which has potential immunomodulatory functions, with domestic SPF pig-derived placental extract for side effect management is being researched for further improvement of quality of life (QOL).
If you have any questions, please contact us.
*Research is also being conducted on the application of specific Cordyceps fungi to humans, which is expected to have immunomodulatory functions.
There are no anticancer drugs exclusively for animals available.
