Side Effects of Chemotherapy

Non-Steroidal Anti-inflammatory Medications (NSAIDs) and Painkillers are used to treat cancer or cancer pain. They may be contraindicated in pets with kidney disease. NSAIDs need to be administered with food or on a full stomach because they may upset the stomach. Please stop steroids if your pet does not eat, vomits or has diarrhoea and seek veterinary advise. Paracetamol and other pain killers such as tramadol, gabapentin, amantadine and/or bisphosphonates may be used as alternative or additional pain killers in pets who do not tolerate NSAIDs or when NSAIDs are not enough to control pain.

Infection and Fever: Most chemotherapy drugs may weaken your pets immune system by lowering the number of white blood cells (neutrophils) for one to two weeks after chemotherapy. As such it important to collect a blood sample to check blood cells prior to each round of chemotherapy; treatment may need to be delayed if the number of white blood cells is low and has not yet recovered from the previous treatment.

An infection may cause a pet’s temperature to rise. Most dogs and cats with a high temperature are miserable and refuse to eat. If your pet is depressed, has a fever or has any blood in the faeces, please seek medical advice promptly as it may be necessary to start treatment with antibiotics and/or intravenous fluids (i.e. a drip). While receiving chemotherapy your pet is at increased risk of developing sepsis (blood infection) which can be a life threatening complication. Once your pet starts antibiotics, to the course of treatment must always be completed as prescribed, even if the situation improves rapidly, as it often will.

Vomiting once or twice (without any other signs or fever) does not usually require treatment. If it continues for more than 24 – 36 hours, or if your pet vomits more than four to six times in a day, please contact us. Withdrawing food and water for a few hours may be helpful, although water should not be restricted for any longer. Once your pet is able to drink without vomiting, you can offer small amounts of bland food such as fish or chicken for a day or so, before gradually returning to a normal diet. Severe vomiting means your pet might require hospitalisation and further treatment, including intravenous fluid therapy and drugs to control nausea.

Fortunately most pets do not develop vomiting, while nausea is more frequent. This may present as a decreased or fussy appetite, a change in food taste, salivation or lip smacking. The Oncologist may administer an injection of the anti-nausea medication maropitant (Cerenia@) concurrently to administration of the chemotherapy; the effect lasts 24 hours and further Cerenia tablets can be administered at home if/as needed in the following days. Should this not be sufficient other medications can be added or used alternatively such as ondansetron, metoclopramide, ranitidine and/or omeprazole.

Diarrhoea without vomiting or fever can usually be managed by feeding a bland diet (fish or chicken with white rice or potato) and then gradually switching back to the food you normally give. Cats can be fed chicken or fish alone without the rice or potato. Should the diarrhoea persist or be severe the Oncologist may prescribe a course of probiotics and/or antibiotics and/or loperamide (Imodium@); please do not administer the latter unless instructed by your veterinary surgeon due to its different mode of use in pets compared to humans. The chemotherapy vincristine may cause constipation especially in cats.

Cystitis: Signs of bladder discomfort (straining to urinate, urinating small amounts frequently, and blood seen in the urine) may occur occasionally after cyclophosphamide chemotherapy treatment; cyclophosphamide in fact is eliminated in the urine and may irritate the bladder. Please call us if you see any of these signs and try and collect a urine sample for analysis. In order to reduce the risk of cystitis developing, cyclophosphamide will be administered with a water tablet called furosemide. Please make sure your pet has plenty of fresh water available at all times, and has frequent opportunities to urinate. Ideally cyclophosphamide should be administered in the morning so that your pet can have access outside during the day.

Hair loss: Only dogs with continually growing hair coats (e.g. Poodles, Old English Sheepdogs, some Terriers) tend to lose significant amounts of hair, although other breeds can sometimes be affected. Cats may lose their whiskers. Hair coats will often return when treatment is finished or with a decrease in frequency of chemotherapy administration, but it may take some time for full recovery. A different colour and texture of hair may regrow. Fatty acid supplements can be administered by mouth or as spot on to improve the quality of your pet coat during treatment. Moistening shampoo such as Epi-soothe may be used to nourish your pets coat and decrease itching. Medicated shampoo may occasionally be needed to control skin infections. Flea, tick and worming treatment must continue as normal.

Liver Disease: Some medications such as prednisolone (steroids), lomustine, masitinib and toceranib may cause some liver damage hence why pets receiving these medications need regular blood tests to check for increase in blood liver parameters and may be prescribed medications to protect the liver. These changes are usually reversible if spotted and treated early and may require temporary or permanent discontinuation of the chemotherapy drug with use of alternative chemotherapies.

Kidney Disease: Certain medications may potentially cause damage to the kidney function and so kidney function needs to be closely monitored by repeating blood tests and urinalysis prior to administration of these medications. Examples of these drugs are non-steroidal anti-inflammatory drugs, the chemotherapy epirubicin and lomustina in cats, masitinib and toceranib, cisplatin (but not carboplatin), and pamidronate.

Increased Blood Pressure: An elevation in blood pressure can be found in certain cancers, with age and kidney disease and has also been caused by certain medications such as toceranib (Palladia@), and so a pets blood pressure is checked as part of general health screening and monitored during treatment.

Tiredness: Cancer itself and most chemotherapy medications have the potential to make your pet feel more tired. Although it is important that your pet continues to enjoy regular exercise, please avoid strenuous exercise or exercise beyond what your pet feels up to doing if your pet feels tired.

Allergic Reaction: Allergic reactions may be caused by intravenous administration of contrast, a dye that is injected to highlight cancer lumps within the body when a CT scan is performed; these reactions are however uncommon.

Allergic reactions may also be seen during or soon after administration of certain chemotherapy drugs. In order to decrease this risk they will be administered slowly with fluids over a period, anti-histamines may be administered before chemotherapy or your pet may stay in hospital for few hours after administration to make sure that he/she is ok such as with use of the chemotherapy L-asparaginase.

Lung and Skin Toxicity: Inflammation of the skin (dermatitis) and lung scarring (pulmonary fibrosis) have been uncommonly reported with administration of rabacfosadine (Tanovea@) and so the Oncologist will advise thata chest x-ray is performed before administration of this drug and to repeat them regularly thereafter. Tanovea cannot be used in pets with pulmonary fibrosis or a history of chronic pulmonary disease that could lead to fibrosis. Tanovea cannot be used in West Highland White Terriers and should be used with caution in other Terrier breeds due to potential genetic predisposition to the development of pulmonary fibrosis.