Glossary
- Carboplatin (Paraplatin®) is used to treat many different cancers in dogs and cats. This drug was specifically developed as an analogue to cisplatin, and has much less gastrointestinal and renal toxicity compared to the parent drug. Carboplatin is often given in combination with doxorubicin (Adriamycin®), and is part of treatment protocols used for many carcinomas including transitional cell carcinoma of the bladder and apocrine gland adenocarcinoma of the canine anal sac. It is also commonly used to treat sarcomas, especially canine osteosarcoma. Carboplatin causes very little gastrointestinal toxicity compared to many other chemotherapy drugs, and does not cause renal injury like cisplatin. However, it can cause bone marrow suppression with low white blood cell and platelet counts. This complication is usually seen 10 to 14 days after treatment in dogs, but can be delayed to as long as 21 days in cats.
- Cisplatin (Platinol®) is a platinum-containing chemotherapy drug with a wide spectrum of activity against many tumours. It can be used to treat different types of carcinoma, and it is arguably the single most effective drug for the treatment of canine osteosarcoma. However, cisplatin is challenging to administer because of its potential toxicities. It cannot be used systemically at any dose in cats, because it causes fatal pulmonary edema. In dogs, cisplatin causes severe nausea and vomiting within minutes of injection unless animals receiving it are pretreated with antinausea drugs. Cisplatin can also result in kidney damage unless it is administered along with large volumes of intravenous fluids. Dogs receiving cisplatin are admitted to the hospital the day before they are due for cisplatin treatment to receive the extra fluids they need.
- Chlorambucil (Leukeran®) is used primarily to treat mast cell tumours and some types of leukemia in dogs; cats with low grade lymphoma may also receive this drug. Chlorambucil is sometimes used as a substitute drug in dogs with lymphoma that develop cystitis after receiving the chemotherapy drug cyclophosphamide. Chlorambucil is generally very well tolerated, and causes very few side effects. However, it can occasionally result in bone marrow suppression so animals that receive it must have blood work done at regular intervals to make sure that white blood cell and platelet counts remain normal. Chlorambucil is only available in an oral form, usually pills, and is often prescribed to be given daily at home. Owners that are giving chlorambucil to their pets must take care to limit their own exposure to this drug. Chlorambucil tablets should never be broken or crushed.
- CCNU or lomustine (CeeNU®) is used to treat mast cell tumours in dogs. It is also used as a rescue drug to treat dogs whose lymphoma has come out of remission after their initial therapy. Although the gastrointestinal side effects of CCNU are usually quite mild, it can cause two other problems: bone marrow suppression, and liver injury. Both white blood cells and platelets can be significantly suppressed by this drug, so it is important to monitor counts very closely. Blood tests are also used to identify hepatic toxicity from CCNU. This damage is usually reversible as long as it is diagnosed early; dogs receiving this drug are also treated with S-adenosylmethionine so that hepatic complications can be minimized as much as possible.
- Mechlorethamine or nitrogen mustard (Mustargen®) is part of the lymphoma rescue protocol "MOPP." Besides Mechlorethamine, the other drugs included in this regimen are vincristine (Oncovin®), Prednisone and Procarbazine. At WVCC this protocol is our first choice for dogs with lymphoma that have lost remission after initial therapy, so most dogs with lymphoma receive MOPP at some point during their course of treatment. The primary toxicity associated with mechlorethamine is bone marrow suppression and low white blood cell counts; if this problem is not quickly identified and treated with antibiotics then serious or even life-threatening infections can occur in affected dogs. Mechlorethamine also causes severe tissue inflammation, necrosis and ulceration if it is not given directly into a vein using a carefully placed intravenous catheter.
- Mitoxantrone (Novantrone®) is an analogue of the commonly used chemotherapy drug doxorubicin (Adriamycin®). The toxicities associated with these two drugs are very similar, with one important exception: mitoxantrone causes significantly less cardiac toxicity when compared to doxorubicin. Doxorubicin is almost always the first choice drug, but in animals where there are concerns regarding cardiac function mitoxantrone may be substituted into the treatment protocol in its place.
Prednisone, a corticosteroid, is one of the least toxic of all commonly used chemotherapy agents. It is not actually a chemotherapy drug in the sense that it kills cancer cells, except in the case of lymphoma where it is directly toxic to malignant lymphocytes. Prednisone also has many other uses in veterinary medicine. It is well tolerated by most pets. It commonly causes increased thirst, urinations, and appetite. With long term use, it can injure the gastrointestinal lining and cause stomach ulcers and colitis. It also suppresses the immune system.
- L-asparaginase (Elspar®, Kidrolase®) is an enzyme that is used to treat lymphoma and some lymphoid leukemias. At the Western Veterinary Cancer Centre, it is often given concurrently with the chemotherapy drug vincristine. The most common side effect seen with L-asparaginase is bone marrow suppression followed by low white blood cell counts that usually develop within 48 to 72 hours of administration. In rare instances, L-asparaginase can cause vomiting due to pancreatitis. Since it is a protein, there is a possibility that an animal can have an allergic reaction to it after repeated doses. Animals receiving more than one dose of this drug are always pretreated with corticosteroids and diphenhydramine (Benadryl®) to prevent problems, and they are closely monitored after their treatment.
Vincristine (Oncovin(R)) is also used most commonly to treat lymphoma and lymphoid leukemia. It is well tolerated compared to many other chemotherapy drugs, and causes relatively little bone marrow suppression in most animals. Some dogs will experience delayed gastrointestinal side effects with vomiting and diarrhea that generally occur 7 to 10 days after treatment. Vincristine causes severe tissue inflammation if it is not given directly into a vein using a carefully placed intravenous catheter.
- Cyclophosphamide (Cytoxan®) is used primarily for the treatment of lymphoma, and occasionally in combination with other drugs to treat some types of carcinoma. It can suppress the bone marrow and cause low white blood cell counts 7 to 10 days after it is given. Animals experiencing this side effect will be weak, lethargic, stop eating, and may have vomiting and diarrhea. This complication is treatable, but immediate antibiotic therapy is needed to prevent life-threatening systemic infection. Occasionally, cyclophosphamide can cause inflammation of the bladder lining in dogs, leading to bloody urine, straining, and frequent attempts to urinate. This condition is called "cytoxan cystitis." An intravenous diuretic is given to all dogs receiving this drug, to encourage rapid elimination of the drug from the body and decrease the likelihood of problems. In the rare cases where cystitis still occurs, cyclophosphamide is removed from the treatment protocol and a different drug is used instead.
- Doxorubicin (Adriamycin®) is one of the most potent and active chemotherapy agents ever developed. It is used to treat a wide variety of cancers including lymphoma, leukemia, carcinomas and sarcomas including osteosarcoma. Bone marrow suppression is more likely with this drug than some others, and low white blood cell counts requiring antibiotic therapy can be seen 7 to 10 days after treatment. Occasional animals may also experience direct gastrointestinal side effects, with nausea, poor appetite, vomiting and diarrhea that usually develops 24 to 72 hours after therapy. Effective antinausea drugs can be prescribed to treat these symptoms when they occur, and they can also be used to prevent them after future treatments. High doses of doxorubicin can cause serious cardiac side effects in dogs and people, and all dogs receiving this drug at WVCC are carefully monitored with electrocardiograms prior to every treatment to prevent this problem. Doxorubicin causes severe tissue necrosis, inflammation and ulceration if it is not given directly into a vein using a carefully placed intravenous catheter.
