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

Why use stomach medication for mast cell tumors?

Updated: January 15th, 2020

Many dog lovers are coping with a diagnosis of canine mast cell tumor.  Just yesterday afternoon I was removing a very large one from the body wall of Big, a 10 year old, 105 pound, much-loved mixed breed.

The day before his surgery, Big started to throw up.  He became quite sick, and would not eat.  His tumor, which was about 5 inches in diameter, had started getting very painful, red and inflamed.

Luckily, tumor is now out and Big is on his way to happier days.

One of our strategies is to help Big with his nausea.  I was explaining to his owner last night that the mast cells in the tumor secrete a substance called histamine, which is the same stuff that causes a bee sting to become red, swollen and painful.

These high histamine levels now in Big’s bloodstream cause the lining of the stomach to produce excess acid.  When you have a belly full of acid, it feels awful and you may start vomiting.

So in dogs with any signs of decreased appetite, nausea (licking lips a lot, salivation), vomiting, or loss of energy with mast cell tumors, we always want to address this acid issue.

There are several approaches.  We definitely want an antacid.  Cimetidine (Tagamet) is a good choice, as this drug has not only antacid effects but also some nice, documented anti-cancer effects.  Tagamet is available over the counter at most locations where non-prescription human medications are sold.  Like many drugs we use in veterinary medicine, it is labeled for human use.

Fresh ginger is always a nice supplement to use in dogs with nausea, and has been shown in papers to help in human medicine with both anti-cancer effects and helping nausea. Many big-box grocery stores will carry ginger root, and some health food stores do as well.

For more information on Mast Cell Tumors, get a copy of the Dog Cancer Survival Guide

Many clinicians advise famotidine (Pepcid), which has a good antacid effect, but no anticancer effects.  You can get Pepcid AC over the counter at most places where non-prescription medications for people are sold.

In cases where there is no other option and the vomiting is very severe, a drug called Zofran (odansetron) can be used.  It is rather expensive, and its use is on the new side.  It does help though for cases where the stomach upset is really bad.  It is a prescription medication.

If there is diarrhea, which reflects inflammation of the intestine (lower down the digestive tract than the stomach), misoprostel (Cytotec) should be considered.  This drug stimulates the protective lining of the intestine and decreases inflammation of the intestinal wall. This is a prescription medication.

Slippery elm, which is from bark of the slippery elm tree, is a good supplement that can be added for diarrhea as well.  It acts as a natural bandage, coating the lining of the intestine and helping soothe and heal.  Slippery elm is available on-line and at health food stores.

Branched chain amino acids can also be added as a part of the arsenal.  These supplement the other approaches by providing the building blocks to rebuild the lining of the intestine.  Branched chain amino acids are available in health food stores and supplement outlets.

Probiotics can always be added to help a bit with diarrhea.  A probiotic is a bacteria which helps restore the normal amounts of healthy bacteria in the intestine.  We need these bacteria, and so do our dogs. These can be purchased at supplement outlets and health food stores.

Lastly, plain old liquid Pepto Bismol helps a lot with diarrhea as well, and is available over the counter too.

For more information and specifics on these items, you can find more details on dosage and use in The Dog Cancer Survival Guide and through discussions with your vet or oncologist.

All my best,

Dr D


Leave a Comment

  1. Shelley Eckersley on April 5, 2019 at 5:52 pm

    My dog has lymphoma, can I give him Benadryl and Tagamet while he is on chemo (CHOP)?

    • Dog Cancer Vet Team on April 8, 2019 at 7:37 am

      Hello Shelley,

      Thanks for writing. As Dr. D writes in the Dog Cancer Survival Guide, certain drugs can affect the metabolism of chemo drugs. You will have to check with your veterinarian on what you can safely use alongside your dog’s current treatment plan.

  2. Gail Wilson on February 7, 2019 at 7:39 am

    Thank you for this article about mast cell tumors. We have a malti-poo that is on Benadryl and 1/2 Pepcid daily. We would like to switch her to Tagamet but don’t know the dose…she weighs 15 pounds. Would you be kind enough to provide this info to us. Thank you in advance.

    p.s. what do you think about giving a dog Kefir for digestive issues?

    • Dog Cancer Vet Team on February 8, 2019 at 7:03 am

      Hello Gail,

      Thanks for writing. In the Dog Cancer Survival Guide, Dr. D provides information and the recommended dosage for Cimetidine on pages 145-146. We can’t advise you about kefir, since Dr. Dressler hasn’t written about it, and we aren’t vets here in customer support.

      Kefir is a trendy way to get probiotics into the diet, but whether it is specifically good for dogs we just aren’t sure.

      Probiotics are good for gut health in general, but they don’t have specific anti cancer effects, which is why Dr. D doesn’t list them as must-consider supplements.

      You would have to talk with your vet to see if you can use Kefir with your dog 🙂

      We hope this helps!

  3. Tarun Grag on June 17, 2014 at 1:30 am

    Thank you for sharing your valuable information.this information very useful for online learners medication for cancer

  4. Betty Hamilton on February 15, 2012 at 5:51 am

    Dear Dr. D.
    My 9 yr. old pug has 4 mast cell tumors. These were tested in Aug. when he had surgery for bladder stones. He had already had surgery on both back legs earlier. I have your book and it is wonderful. After much soul searching we decided against surgery. He is on benadryl and and anacid. I have him on Apocaps and K9. His stool is now semi loose and soft but not watery and gold or yellow in color. I have just this week taken him off Apocaps and K9 to see if this helps. His feed has to be Hills U/D because of the stones.He has not lost weight and has no other noticible symtoms. What can I do to firm his stools. My vet is very kind and sympathize but has admitted she knows nothing about pet nutrition. Thanks for you book and guidance. B

  5. Kimberly on February 13, 2012 at 8:54 am

    Hi Dr. D,
    My 8 year old mix breed just had two mast cells (grade 2) removed last week and since the operation has steadily had severe bouts of diarrhea. He has been put on Pepcid and we have been feeding him boiled chicken and rice only for his meals. It doesn’t seem to be getting any better. We have an appointment with his new oncologist on Thursday but his regular vet told us it was likely from the anesthesia and the pain killer used, as well as stress. Is it more likely, however, to be the result of histamines released during the procedure? Thank you for all of your great information.

  6. margaret on June 15, 2011 at 3:21 am

    I just came upon your web-site.. It does seem to have very useful info.
    My dog does have the mast cell tumors. I’ll talk more about that @ a lster date.
    till–then.. Margaret………………

  7. Lindsay on April 26, 2011 at 1:07 pm

    Hi Dr. D,

    I just found your very informational blog today and a week after our family’s 14 year old labrador was diagnosed with very aggressive mast cell cancer. I wish I had found this site longer ago because his prognosis is not good and the battle is day to day at this point.

    However, I also have a 4 year old boxer. After reading the many posts by you and others it has made me think about all of her issues over the past 4 years. I can’t tell you the amount of pepcid, benadryl, and pepto she has had since a pup. She has always had a sensitive GI with bouts of vomiting and diarrhea. We have had a few vets and even a holistic vet and all attribute her sensitivities to some type of allergic reaction (I feel it’s environmental, as does my current vet but the allergy tests did not come back strong in any environmental area). I have even noticed other reactions in her such as being more “down,” quiet, whiny, urine accidents in her crate, vomiting, etc when she seems to be having a reaction.

    Is there a higher chance of mast cell tumors in dogs with allergy issues? She has been fairly stable lately but has bouts of allergic reactions and most recently has had irritations on the skin folds of her face which she itches to death and causes them to bleed, and has had to have antihistamines and sometimes antibiotics for infections. Her bowels have been stable for a good 2 years since switching to the proper food for her needs- California Natural Herring and Sweet Potato. The throwing up has been minimal and pepcid usually fixes it but I definitely want to try Tagamet based on your suggestion of anticancer properties.

    I guess what I’m getting at is that she has allergy issues(to what?- we aren’t exactly sure)- bottom line and they creep up every so often- some more severe than others. I hate medicating her but is it better to put her on an antihistamine as needed to calm her body from worse harm? Is there any way to prevent mast cell cancer and what do you think about her issues or is she just a “sensitive” dog with typical “boxer issues”?

    Also, have you heard of Moducare? She has been on it daily for 2 years or so as prescribed by her holistic vet we see occasionally for alternative meds. This was suggested as an immune system booster for her when she was about 1 1/2 years old and having many digestive issues to help support her immune system.

    Looking forward to what you suggest/think. Your blog is wonderful and so informative. I am thinking about getting your book just to be educated as I am such an animal lover and always wanted to be a vet as a kid!

    Thanks for your time,

    • DemianDressler on April 27, 2011 at 10:19 pm

      Dear Lindsay,
      there seems to be a bit of a link, although a soft one, between allergies and mast cell tumor. You might consider allergy testing and a true hypoallergenic food trial and possibly immunotherapy. And if you are a dog lover and a boxer guardian, the Guide would be a smart idea…

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