agents in each species. Doxorubicin, for example, is not a good choice for a dog with congestive heart failure/myocardial disease, but is also a poor choice for a cat with renal failure. Dogs receiving long term CCNU therapy need to be monitored for liver disease (chronic effect of this drug in some dogs).  If renal/hepatic function is compromised, drugs that are metabolized or eliminated by these organs will need dose adjustments as their half lives in circulation may be prolonged.
6. Urologic toxicity. Cyclophosphamide and ifosphamide can both cause sterile hemorrhagic cystitis, a painful condition that mimics a severe bladder infection in clinical signs.  Cyclophosphamide  should not be given to dogs showing signs of lower urinary tract disease.  While this side effect is most common with chronic cyclophosphamide administration, it is an occasional acute effect. Co-administration with prednisone is somewhat effective as a preventative.  Ifosphamide should never be given without MESNA concurrently to prevent cystitis.
7. Hair loss.  Only some chemotherapy drugs can cause hair loss in some veterinary patients.  Doxorubicin, liposome-encapsulated doxorubicin,  and taxol are the major culprits. Poodles, bichon frises and their mixes are the most susceptible to hair loss, although there are individual dogs where thinning haircoats can be seen (I have seen this problem in the occasional Briard, Golden Retriever, Schnauzers, and Labs).  Often when we see hair loss in breeds like labs or golden retrievers, they have underlying pruritic allergic dermatitis, and the places that they rub become bald as the growth rate of their fur has been slowed by the chemotherapy. Chemo alopecia cannot be treated or prevented.  Pruritic skin disease (except in the case of liposome-encapsuled doxorubicin) is NOT caused by chemotherapy - there must be an allergic dermatitis, scabies, pyoderma, or other cause. Whisker loss in cats is common with doxorubicin treatment, although hair loss is rare.
8. Knowing breed related problems.  Shetland Sheepdogs and giant breed dogs (Deerhounds, Wolfhounds) are more likely to have chemotherapy problems than other breeds of the same size. We routinely adjust doses and use prophylactic medications in dogs like these.
9. Adjusting doses/altering drugs if side effects occur that cannot be prevented. No chemotherapy protocol is set in stone. All protocols can be adjusted to meet individual needs.

By following these simple steps, we all can try to make certain that few dogs or cats have "human-like" chemotherapy experiences.

Chemotherapy Side Effects
Sarah E. Sheafor, DVM, Diplomate, ACVIM (Oncology)

There are very few words in the English language with quite as much emotional baggage as the words "cancer " and "chemotherapy".  I routinely see clients who start out their conversations with me by saying that while they want to hear what I have to say about their pet's cancer, they feel that giving chemotherapy is cruel and inhumane (or words to that effect). In veterinary oncology, our goal is to maintain a normal quality of life at all times.  How can we help all of our patients on therapy to be happy, eating and normal at home?

1. Correct dose.  This point seems to be an obvious one in that we should always weigh each patient prior to each treatment, and recalculate the amount of drug based on the scheduled dose, but the issue is actually more complex.  For example, the body surface area chart is inaccurate for dogs under 20 pounds if they are being given doxorubicin, carboplatin or melphalan, (and possibly other drugs as well).  These drugs need adjustments in the dose (ie, decreasing the dose of doxorubicin to 25mg/m2 from 30mg/m2 in a miniature poodle).
2. Correct dose for the species.  Cats, as we all know, are not small dogs.  Using dog doses in cats will result in unacceptable toxicity when we administer doxorubicin, carboplatin and vincristine.
3. Prophylactic antibiotics when using myelosuppressive chemotherapy or doxorubicin.  When we can predict that many patients will become severely neutropenic (<1200 neutrophils) following administration of a drug or drug combination, administration of a broad spectrum antibiotic can be helpful.  CCNU, doxorubicin/dacarbazine, and high dose carboplatin, are all examples of drug therapy where we will see at least one in five dogs become neutropenic 5-10 days after therapy.  A study presented at last year's VCS meeting proved that administering sulfa-trimethoprim to all dogs after standard single agent doxorubicin chemotherapy resulted in many fewer dogs developing gastroenteritis as well as fewer dogs developing sepsis.
4. Anti-emetics.  Different chemotherapy drugs cause nausea/vomiting or diarrhea in different ways.  In order to prescribe an effective anti-emetic, we must first understand the mechanism of toxicity. For example, cisplatin activates the chemoreceptor trigger zone as it is being administerd, so drugs designed to block that pathway of nausea (IV butorphanol, ondansetron, dolasetron) are the most effective and are given prior to the cisplatin administration.   In contrast, those few dogs who develop nausea/vomiting or diarrhea after doxorubicin treatment most commonly do so 2-4 days after the chemotherapy is given. The mechanism of the vomiting/diarrhea is that the chemotherapy kills the gut crypt enterocytes, so several days later, the villus tips in the small intestine are denuded (similar to viral enteritis).  Carafate and pepcid will not help as the problem is rarely gastric.  Peptobismol is often very helpful, as is metoclopramide. If this side effect of doxorubicin occurs in one patient, that same patient will develop the problem with subsequent doses of doxorubicin. Prevention by using glutamine (an essential amino acid for gut enterocytes) and peptobismol beginning prior to the next chemo and continuing for 4 days after that chemo is usually successful. 
5. Monitoring for complications/picking the right drug for the patient.  We must know the organ toxicities of chemotherapy