Cyclophosphamide for Dogs

by Catherine Troiano
Cyclophosphamide may play a crucial role in your dog's cancer treatment.

Cyclophosphamide may play a crucial role in your dog's cancer treatment.

Janie Airey/Digital Vision/Getty Images

If your dog has been diagnosed with an immune-mediated disease or a certain form of cancer, such as lymphoma, your veterinarian will speak to you about available treatment options for your furry friend. There are a number of drugs that he may mention, one of which is called cyclophosphamide. This drug is traditionally administered as part of a chemotherapy regimen that implements the use of several drugs.

The Treatment Role of Cyclophosphamide

Cyclophosphamide is a powerful drug and one of the big guns used in combating serious illnesses. Cyclophosphamide, commonly known as Cytoxan, is an immunosuppressant drug used to treat conditions, such as cancers of the blood cells and bone marrow, immune-mediated hemolytic anemia, systemic lupus erythematosus and vasculitis. Cyclophosphamide functions as an alkylating agent, meaning that once it is administered, it binds with DNA and destroys the body’s most rapidly dividing cells, including cancer or inflammatory cells. The drug is derived from a similar nitrogen mustard base that is found in the chemical weapon used as mustard gas.

Side Effects of Cyclophosphamide

One of the side effects of cyclophosphamide is bone marrow suppression, in which the white blood cell count drops. Since white blood cells fight infection, this effect can leave dogs vulnerable to infection. During treatment with cyclophosphamide, your veterinarian will repeat blood cell count tests to ensure that your dog’s white cells do not dip too low. Blood tests help your veterinarian to maintain a therapeutic balance of the drug, preventing the dog from becoming more sick, while maximizing his chance of remission. Other potential side effects of the drug include gastrointestinal upset, a decrease in appetite and hemorrhagic cyctitis, which causes blood in the urine. Be sure to report all new symptoms or unusual findings to your veterinarian immediately.

Warnings and Precautions

Cyclophosphamide is fatal to the rapidly dividing cells of a developing fetus, and should not be administered to a pregnant dog. The drug must be used with caution in dogs with renal disease because the kidney filters the drug and excretes it through urination. Cyclophosphamide may react with certain medications, including phenobarbital and thiazide diuretics, so be sure to remind your veterinarian of any drugs that your dog normally takes. If you are instructed to administer cyclophosphamide tablets to your dog at home, wear gloves when handling the drug.

Two Types of Therapy

Canine lymphosarcoma, or lymphoma, is one of the most prevalent forms of cancer to strike dogs. Treatment typically consists of multiple chemotherapy drugs that may include vincristine, doxorubicin and cyclophosphamide. These drugs are administered over the course of several treatment sessions at periodic intervals. Alternately, cyclophosphamide may be used in smaller, daily doses as part of a treatment protocol known as metronomic therapy. The smaller dose minimizes side effects, and the frequency of administration launches a daily assault on the cancerous mass. Lymphoma responds favorably to chemotherapy. Most dogs tolerate chemotherapy exceptionally well and the majority will experience remission. The sooner your dog is diagnosed, the more effective chemotherapy will be, so always have your veterinarian examine any new lumps and bumps as soon as you find them.

Photo Credits

  • Janie Airey/Digital Vision/Getty Images