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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

The Oncologist’s Perspective on Chemotherapy and Gastrointestinal (GI) side effects: Part One

Updated: October 5th, 2018

Obviously, you are concerned about your dog having side effects from chemotherapy.  No one including me, the oncologist, wants your dog to get sick.

Chemotherapy targets rapidly dividing cancer cells. However, there are normal cells in the body that also rapidly divide as part of their normal function. It is these cells that can be expected to be potentially damaged from chemotherapy. The most common side effects from chemotherapy are GI (gastrointestinal) discomfort and bone marrow suppression (typically a decreased white blood cell count). In some breeds, there can also be hair loss. Today I will talk about GI side effects.

GI side effects include loss of appetite, nausea, vomiting, or diarrhea. Unlike people, most dogs rarely get sick during treatment itself or the day of treatment. The majority of GI side effects typically occur 2 to 5 days after treatment and typically last 1 to 3 days – while the small intestine is busy replacing the damaged cells with brand new cells. So the GI side effects are temporary, and (happily) mild in most dogs.

Most vomiting and diarrhea can be managed at home. For my patients, they go home with “just-in-case medications” on the first day of chemotherapy with a detailed set of instructions, because I want them to be prepared. That way, if nausea, vomiting, or diarrhea occurs at 10 pm on a Sunday night, the medications can be started without having to find an open veterinary clinic. With early intervention, the vomiting or diarrhea will resolve quicker, and your dog will get back to normal sooner.

I call these “just in case” medications because most dogs do not need GI medications with many chemotherapy drugs like Elspar, vincristine, cyclophosphamide, carboplatin.  If your dog does experience side effects with the first treatment, though, it makes sense to use anti- nausea medications and/or anti-diarrhea medications during and after subsequent treatments as a rule.

Doxorubicin is the exception to this rule. A recent study showed that dogs receiving oral Cerenia with doxorubicin (aka Adriamycin) experienced significantly less vomiting and diarrhea during the week following doxorubicin compared to when the same dogs received placebo after the chemotherapy. So I do recommend the use of Cerenia for the 4 days after doxorubicin in all cases.

Rarely, the vomiting and diarrhea may be so severe after chemotherapy that we worry about dehydration. We will talk about hospitalization due severe vomiting and diarrhea in my next blog. You can learn more about GI side effects and Full Spectrum ways to manage them in the Dog Cancer Survival Guide.

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  1. Denise on February 23, 2013 at 3:27 pm

    We euthanized our dog this evening. His platelet count did not improve (it was only 4,000), and his prognosis was very poor. So we gave him one last act of kindness.

    In looking through his records, I noticed that he was given nearly a full dose of carboplatin. We didn’t authorize that. We authorized a half dose because the half dose of mitoxantrone he received previously hit him pretty hard (he became septic), and his kidney function values were less than optimal. Dr. Portela apparently ignored our request.

    If we had it to do over again, we would simply have used Apocaps and K-9. The chemo was just too hard on him. I wish our dog’s oncologists had been more willing to adopt a more integrative approach to his treatment rather than adopting an adversarial stance. I copied abstracts from Medline on scientific studies showing the efficacy of the ingredients in Apocaps for cancer treatment and left it with the ER vet to put in his file.

    We are very grateful for the kindness and open-minded the ER veterinarians showed us and our dog during his last hours.

    • Dr. Demian Dressler on March 6, 2013 at 4:51 pm

      I’m really sorry Denise. Ugh.
      So sorry.

    • Dr. Susan Ettinger on March 11, 2013 at 7:17 pm

      I too extend my sympathies to you and your family. Know that you did all you could for him. He was lucky to have such a dedicated family. So sorry for your loss.
      With sympathy, Dr Sue

  2. Denise on February 23, 2013 at 5:46 am

    Dr. Sue, Thanks for the reply. We did lower the Apocaps dose (to half) and gave him his first dose of mirtazapine yesterday. But he is in the ICU now. His platelet count is dangerously low, and his WBC is very high. He has blood in his stool and his gums, so he is probably hemorrhaging. They are trying to stabilize him, but we are probably going to have to say goodbye today.

    Our oncologist, Dr. Portela of the University of Illinois Veterinary Teaching Hospital gave us a pretty good tongue lashing yesterday, saying it is our fault for putting him on Apocaps and that she will make sure no other animal in her care ever takes it. According to her, she has treated hundreds of animals with metastatic cancers and none of them has ever responded so poorly to chemotherapy. So essentially, she told us that we killed our dog by using Apocaps.

    We told the oncology team from the beginning that we wanted to use Apocaps and K-9 along with the chemotherapy, and essentially begged them to go to the Apocaps veterinary portal so that they would be familiar with these nutraceuticals and how they may affect chemotherapy protocols. But I am sorry to say that the response we got was pretty much the same as Galileo got when he asked the clergy to look into his telescope. Dr. Portela flatly stated that there was no evidence that these types of supplements work, and they were plainly hurting our dog rather than helping him.

    I finally contacted Apocaps myself yesterday and was told Dr. Dressler would be willing to have a phone consultation with our vet. My husband called Dr. Portela and insisted that the consultation be pursued, so she passed the request on to one of the senior oncology veterinarians because she sees no point in consulting about a supplement that is killing our dog. But it looks like we’re too late.

    Dr. Portela’s attitude last evening in the ER was one of smug triumph that our dog had taken such a turn for the worse. I can’t describe how painful that was for my husband and me. The ER doctor was much more compassionate and suggested a treatment regimen to see if his platelet count could be boosted. We are still waiting to hear about the results, but according to the ER doctor who called us this morning, the prognosis is not good. So we may have to euthanize him.

    Thanks for listening. For our part, we don’t believe Apocaps harmed our dog.

  3. Denise on February 22, 2013 at 7:10 am

    Well, it looks like I’m not going to get a response to my question, for some reason. If any viewers of this blog can offer some advice, I would really appreciate it.

    I did re-view the videos on nausea, and re-read the relevant blog pieces and sections of the Dog Cancer Survival Guide, which all offered very useful tips. But our dog still is not eating on his own.

    Meanwhile, I’m sorry to say our veterinarian is blaming us for his poor response to chemo because we insisted on continuing the Apocaps and K-9. At this point, we are just hoping he gets a bit of a reprieve once he is past the 14 day carboplatin nadir window. He is now at day 8, and he is having a pretty rough time.

  4. Denise on February 19, 2013 at 7:55 am

    Our dog has refused to eat since his second round of chemo (five days ago). He seems hungry and has pretty good energy, but when we offer any kind of food, he sniffs it and turns away as though it makes him queasy.

    Our vet prescribed Cerenia, but that didn’t seem to have much effect. Our vet wanted to put him on prednisone to stimulate his appetite, which meant taking him off Apocaps. When we said we preferred to keep him on the Apocaps, nothing else was offered.

    We have been pushing food toward the back of his mouth, and once there, he swallows it. Otherwise, he would not be getting any nutrition at all.

    His first round of chemo included mitoxantrone. Carboplatin was used for his second round. He has metastatic prostate cancer. We chose to treat rather than euthanize because he is still very active and (before the chemo) was still eating and enjoying life. We were hoping to slow the cancer’s progression.

    Any advice on how to get him to resume eating?


    • Dr. Susan Ettinger on February 22, 2013 at 6:48 pm

      Nausea related to chemo typically should resolve by the 1st week after chemo. Other nausea meds to ask for are metoclopromide (Reglan). Also I like the appetite stimulant mirtazapine. If you are beyond a week after chemo and the appetite is still poor, I would stop the Apocaps for a few days. Sometimes, they just need a break for a few days, or lower the Apocaps dose. Ask your oncologist about these other meds.
      Good luck, Dr Sue

  5. Adrianne on February 4, 2013 at 8:41 am

    She also gets fish oil, vitamins and Pepcid which I won’t stop!!

  6. Adrianne on February 4, 2013 at 8:39 am

    This was our first time using doxorubicin this past Wednesday and on Friday my baby came den with diarrhea. I caked the vet and she put her on flaggyl, I thought it was clearing up on Saturday, but yesterday it came back. Not watery but very loose. I cook for her and also incorporate a little bit of Orijen. I’m going to try bland for a few days and see if that helps. She usually gets chicken, veggies steel cut Oates and cottage cheese. I’m going to try just chicken, brown rice and pumpkin for a couple of days. This drug has been the only one that has caused diarrhea and it really bothers me. I love my Salem so much!!

    • Dr. Susan Ettinger on February 8, 2013 at 6:22 pm

      Hi Adrianne,
      The next time through you can ask your vet about starting the Flagyl the day of or the day after chemo. I find that helps in the cases that got diarrhea the 1st time. Also consider a probiotic. I keep some cases on a probiotic throughout chemo. A product called RX Clay is helpful too. Hang in there!
      All my best, Dr Sue

  7. Karen on January 31, 2013 at 5:39 am

    Never got a reply to our post but the diarrohea cleared up with antibiotics and our dog is now in complete remission.Next time I will try the Cerenia after the doxorubicin which comes round in a week’s time.

  8. Karen on January 14, 2013 at 1:54 am

    Dear Dr Ettinger,

    Our 6 year old female Bernese was diagnosed with lymphoma on December 11 and began the Wisconsin protocol on 14 December 2012. Until this week, there were no side effects. She has re-gained 4kg since treatment is now 40kg. On 4 January, she had doxorubicin and 4 days later had a first bout of diahrrohea. Over the weekend, it was on and off (soft but formed stool) and today Monday it is everywhere and definitiely loose.

    We administered the anti-diahorreal medicine given to us (Barexal) but we have to mix this with cottage cheese as she refuses to drink it. Otherwise she is still happy and content (as she has been all along) and really wants to eat (even today).Her last blood test was fine. We were given Cerenia but as she hadn’t had nausea (as far as we can tell) , we did not give her this and I have only now seen your blog which says to adminster it before the doxorubicin.

    My question is whether this is an effect of the drug which seems an obvious thing to say or is it a coincidence that the diarrohea started after we finally got hold of the Hills Prescription Diet P/D (which we were told is an alternative to N/D). I have to say that I bought the Dog Cancer book but I remained confused about diet and supplements. For the first week after diagnosis we cooked the diet, then she seemed to lose a KG (now regained), so we bought Hills I/D and 12 tins of N/D, finally got hold of Apocaps whilst waiting for P/D.In that period, I mixed the commercial with the home cooked and the supplements (Krill oil, garlic, ginger, sardines etc) and she had no problem.

    We live in Belgium btw, hence we have to source Apocaps from the UK but everything else is available here and she is treated at a university hospital.


    My question is could it be the P/D or is it the Doxorubicin?

    • Dr. Susan Ettinger on February 3, 2013 at 11:33 am

      The diarrhea could be the result of doxorubicin or the change in diet, or both. It is recommended to slowly transition any change of diet. As for chemo related diarrhea, it typically occurs 1 to 5 days after chemo and should only last a few days. Good luck!
      All my best, Dr Sue

  9. mary on May 21, 2012 at 9:55 am

    my 12 yr old lab received 6C of alernating doxorubicin and carboplatin for her ca tx and she did quite well on it – I was very happily surprised. However we are just shy of 3 weeks past her last and final tx and she has developed diarrhea and vomitting – could it be related to the chemo this far out?

    • Dr. Susan Ettinger on May 21, 2012 at 4:24 pm

      Hi Mary,
      Glad to hear your lab tolerated treatment so well. =) Typically GI side effects occur 1 to 5 days after treatment, so almost 3 weeks out seems unlikely, and I am wondering if something else is not contributing to the diarrhea? Change in food/diet? Supplements?
      I would talk to your vet about some supportive care like an anti-diarrheal and/or a probiotic. Maybe a bland diet for a few days?
      Good luck!
      All my best, Dr Sue

  10. Mark on November 15, 2011 at 7:58 am

    So far, the worst part of the doxo treatment for our Dane has been about a days worth of loose stools (w/ the ability to happen outside thankfully). Also have used Cerenia as well and after the 4 day when it’s recommended to take a day off is when it occurs.

    This time around I only gave Cerenia for 2 days and no issues as of yet and we are 5 days post treatment.

    thanks again for another good article

    • Dr. Susan Ettinger on November 16, 2011 at 6:09 pm

      Thanks Mark! Glad your dog is tolerating treatment well!
      Also be sure to check your the Dog Cancer Survival Guide for more info and tips. Thanks again for reading!

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