Veterinarians use chemotherapy to give dogs and cats with cancer a good quality of life with minimal side effects.  Most dogs and cats feel good even when they are receiving chemo.

However, the potential for side effects does exist, and varies with the drug used.  Unfortunately, the only way to know whether an animal is going to have side effects is to give the drug.  Some animals never get sick during chemotherapy while others are more sensitive to the drugs.

The most common side effects and their management include:

Decreased Energy or Lethargy

This may be caused by a low white blood cell count, which will often make your pet feel tired.  A low white blood cell count can also make your pet more susceptible to infection.  An increased temperature may indicate the onset of an infection.  To establish the normal temperature range for your pet, please take their temperature twice daily for one week.  Charting this will help you remember their normal range (normal temperature for a dog or cat is 37.5-39.5oC).  If the temperature goes above 39.6oC, please call us.

The easiest method to obtain a temperature from your pet is to take an axillary temperature.  This method involves placing the thermometer deep into your pet’s armpit area and holding the thermometer in place until it provides you with the results.

Signs of lethargy: your pet becomes tired easily, shows reluctance to play, eat, drink or other things that they may have used to enjoy, excessive sleeping, general lack of enthusiasm

Decreased Appetite

Unfortunately, the chemo drugs may make your pet feel nauseous.  This may change their normal eating habits.  There may also be some change to their taste sensation causing them to refuse their regular diet.  You may consider offering different foods that are new and more tempting.  Some suggestions:  lean cooked ground beef or chicken and rice, caned dog foods, chicken broth based baby foods, scrambled eggs, etc.  Heating foods slightly may also help make them more palatable.  We can provide anti-nausea medications if necessary.


If your pet is vomiting frequently and unable to keep water down, please call us.  If the vomiting is infrequent, you may consider starting your pet on an anti-nausea drug.  If they are uninterested in eating at this time, please don’t force them.  Eating is less important, as long as they continue to drink.  You may try offering them bland diets such as lean cooked ground beef or chicken and rice, or a commercial food such as Eukanuba Low Residue Diet.

Examples of medication that may be prescribed for vomiting include metoclopramide, ranitidine (Zantac), famotidine (Pepcid), Cerenia.

Signs of nausea: excessive salivation, lip smacking, excessive licking, showing interest in food but not eating, inappetance.


Ensure a good supply of fresh water is available at all times.  If you leave your pet, it may be better to confine them to an area that is easily cleaned if accidents occur.  A bland diet is recommended for diarrhea as it is more easily digested.  If you see blood in the diarrhea, or if the diarrhea persists for several days, please call us.

Examples of medications that may be prescribed for diarrhea include metronidazole and tylosine.

Hair Loss

Most pets will experience some form of hair loss.  Dogs who need regular grooming (i.e. Poodles, Schnauzers, West Highland Terriers, and Bichons) are often most affected. Other breeds may only experience decreased shedding without noticeable hair loss.  Whiskers and eyelashes may fall out.  Hair loss in generally temporary and most dogs will grow a new and softer coat, and sometimes in a different colour.

Symptoms are expected to occur 3-5 days following treatment.

Chemo drugs are excreted in the urine, feces and vomit for 48-72hrs after treatment. Please wear rubber gloves to clean up any of the above if an accident does occur.

If at any time you feel uncomfortable with the symptoms or side effects that your pet is exhibiting please don’t hesitate to call us.