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An Urban Experience
S. Ettinger1
How I treat vomiting and diarrhea in chemo patients
Sue Ettinger, DVM, DACVIM (Oncology)
Dr Sue Cancer Vet PLLC and Animal Specialty & Emergency Center Wappinger Falls, NY, USA
“Cancer” is a scary word that is often equated with death. There is often a visceral fear of cancer, and pet owners think cancer equals pain and suffering. There are many myths and misconceptions about chemotherapy in pets. Owners think cancer treatment will just make the patient sicker.
But cancer is not a death sentence. With treatment, many cancer patients are not only living longer, but living well. Chemotherapy is well tolerated in the majority of dogs and cats undergoing treatment. Whether you are directly managing chemotherapy patients or sharing cases with an oncologist, there are simple tips and tricks to improve quality of
life and minimize gastrointestinal side effects in chemotherapy patients.
Conventional chemotherapy is typically given at high dosages, known as maximum tolerated dose, or MTD. The goal is to kill the rapidly dividing cancer cells. But some normal cells that also have high turnover often can be temporarily damaged by MTD chemotherapy. The normal tissues that typically are most sensitive
to chemotherapy are the bone marrow, hair follicles (alopecia), and the gastrointestinal lining. This is often referred to as “BAG”. As a result there is a break period to allow these cell populations to recover. MTD is typically given weekly to every 3 weeks.
The overall toxicity rate is very low in veterinary chemotherapy patients. In my experience, only 15-20% experience side effects, and this is even less common in cats than dogs. The primary goal is to provide the best quality of life possible for as long as possible. As I say, live longer, live well. Most side effects are mild and medically manageable.
Gastrointestinal (GI) toxicity
Gastrointestinal (GI) toxicity includes vomiting, diarrhea, decreased appetite, nausea. It typically 1 to 5 days after chemotherapy and is self-limiting – lasting on average 2-3 days. These side effects are less common in feline chemotherapy patients than dogs. I recommend being very proactive with nausea/anti-emetic drugs.
I often will use Cerenia or mirtazapine preventatively and as needed. I recommend giving Cerenia at administration with the following drugs: doxorubicin, vincristine, vinblastine, carboplatin, mitoxantrone, dacarbazine, and the MOPP protocol. If the pet has nausea/vomiting event within 24 hours of administration, I will add Cerenia SQ or IV at the time of administration at the subsequent treatment. For oral chemotherapy being given at home,
I advise the owner give oral Cerenia 1 hour before chemotherapy pill dosing.
I always recommend oral Cerenia for 4 days after doxorubicin in dogs to prevent nausea and vomiting. If there are side effects with other chemotherapeutics, I also typically will add prophylactic medications to prevent side effects like nausea, vomiting or diarrhea as indicated. If the GI side effects are more severe in
a patient, the drug type or dosage may be adjusted at subsequent treatments to minimize the chance of side effects recurring.
Unlike dogs, I do not routinely use GI medications unless the cat had issues with a prior treatment or had GI clinical signs prior to treatment (i.e. GI lymphoma)
For diarrhea, I typically send my patients home with metronidazole and a probiotic. Metronidazole is
a synthetic nitroimidazole with antibacterial, anti- protozoal and anti-inflammatory properties and is commonly prescribed for acute and chronic diarrhea.
It is metabolized and excreted by the liver, so take care with patients with impaired liver function. Neurotoxicity
is associated with higher doses and chronic use, so I do not recommend chronic use. Dose: 15 mg/kg PO BID for 5 days
Rx Clay is a good option for chronic diarrhea and patients needing multiple courses of metronidazole. Rx Clay is a calcium aluminosilicate (CAS), which
is geological nanomaterial that adsorbs bacterial enterotoxins and increases reabsorption of intraluminal water in GIT
Acute vomiting is typically associated with cisplatin, doxorubicin (Adriamycin), dacarbazine (DTIC), cyclophosphamide, actinomycin, 5-FU streptozoticin. This can typically be prevented with pre-treatment

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