P. 654

An Urban Experience
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-in ammatory 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
Delayed vomiting is more common in our patients. This is due to direct damage to rapidly dividing GIT cells (crypt cells) or via the centrally mediated CRTZ stimulated via gut vagal efferents. Delayed vomiting is most commonly 2 to 5 days post-chemo and seen with doxorubicin
and the vinca alkaloids. Clinical signs include vomiting, diarrhea, anorexia, lethargy, weakness, + dehydration.
For work up, I recommend CBC, chemistry panel, UA, +/- fecal  oatation and cultures. If abdominal pain is present, consider AXR or AUS to rule out foreign body, obstruction, and intussusception. For patients with GI neoplasia, it can be challenging to differentiate chemotherapy side effects vs. disease, and a good history can be key.
For outpatient treatment, I recommend NPO, food & water trial, bland diet, anti-emetics, antibiotics with severe diarrhea and a probiotic. Do not forget to discontinue oral chemotherapy or delay chemotherapy treatment. In addition, I recommend prophylactic therapy with the next chemotherapy.
For inpatient, I add injectable antiemetics, IV  uid
therapy, and IV antibiotics. An important note, I strongly encourage owners to NOT EUTHANIZE at this time. It is amazing with 1 to 2 days of good supportive care how quickly these patients improve. And with prophylactic therapy and a dose reduction, these patients can tolerate the same chemotherapy drug.
Myelosuppression and Neutropenia
Bone marrow suppression most commonly results in
a neutropenia but cats seem to be more tolerant than dogs. Neutrophils and platelets are at greatest risk due to the shorter circulating lifespan and shorter bone marrow transit times. Neutropenia is the dose-limiting toxicity in veterinary oncology.
In addition to the chemotherapy targeting
rapidly dividing bone marrow stem cells, other mechanisms for neutropenia includes bone marrow in ltration with neoplastic cells (leukemia, advanced stage lymphoma, multiple myeloma) and increased consumption due to infection.
When a chemotherapy drug is used that is known to have a high potential for bone marrow suppression (like doxorubicin, carboplatin and Lomustine), a complete blood count (CBC) is often checked after the treatment to check the expected nadir (low neutrophil count) and see if antibiotics and/or a dose reduction are needed. I recommend a nadir be checked with all chemotherapy drugs except L-aspariginase.
The nadir typically occurs 7 days after chemotherapy administration. Pay attention to the neutrophil count, not the total white blood cell count. For some chemotherapy drugs the nadir is more variable such as carboplatin
and Lomustine. For cats, the nadir is can occur 7 to 28 days after treatment. In dogs the nadir for carboplatin
in day 10-14. Chlorambucil tends to cause delayed neutropenias and thrombocytopenias after chronic use. Subsequent doses of chemotherapy are adjusted based on the results of the CBC.
Antibiotics may be prescribed as a preventive measure but its use is controversial. Common antibiotics are TMS and Clavamox. I recommend prophylactic use with the more myelosuprressive drugs (doxorubicin, carboplatin and Lomustine) or if the previous nadir was <1500 neutrophils. Unlike dogs, I do not routinely use prophylactic antibiotics unless the cat had issues with a
How Myelosup- pressive?
Chemotherapy Drug
Mildly to not
corticosteroids, Elspar, cisplatin, chlorambucil, bleomycin, vincristine
vincristine, vinblastine, cyclophosphamide, melphalan
doxorubicin, Lomustine, mitoxantrone, carboplatin, combination protocols

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