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

Mirtazapine for Dog Cancer

Updated: May 15th, 2024

Dear Dog Lovers,

A newer drug is being used frequently lately, and I would like to make sure everyone dealing with a canine cancer diagnosis has heard of it.  This medication may help some dogs out there, so let’s keep everyone up to date.

The drug is mirtazapine, also called Remeron.

Now granted, many of the readers of this blog want to know about diet and supplements.  In the spirit of true integrated (full spectrum) medicine, we should look at everything conventional science has to offer, hence this post.

But for those who want to know what supplement I use in my patients, here is the quick answer: Apocaps.  And yes, of course I am biased since I put it together and use it.  It is not a nausea medication, rather it helps to normalize a critical process called apoptosis in the body.

Mirtazapine is a very effective appetite stimulant.  This is particularly useful in cases of canine cancer, especially if either chemotherapy or the cancer itself is causing a loss of appetite.

On top of this, it helps with nausea and vomiting, and helps block spasm of the muscular wall of the stomach and intestine.  This is useful as it not only improves nutrition by keeping food down, but on top of that, alleviation of vomiting is a major life quality positive.

But there’s more.  Mirtazapine has a neat little antihistamine effect.  Dogs with mast cell tumor cells in the body often have histamine excess, since the tumor cells secrete histamine.  Too much histamine is not good for the body, causing swelling, redness, discomfort, nausea, vomiting, loss of appetite, and even low blood pressure. This makes mirtazapine very well suited for some dogs with mast cell tumors.

Finally, this medication is an antidepressant.  Although there is little talk of canine depression’s link to cancer, there are some documented links in human medicine.  In my opinion, the same reasoning may be applied to dogs, being sentient beings with happiness and sorrows like ours.

Mirtazapine was originally designed and intended for use in people for its antidepressant effect.  However, in veterinary cancer care, we take advantage of mirtazapine’s effects on fighting nausea and helping with appetite. The effects on mood and anxiety are a bonus!

Mirtazapine works by increasing two chemicals in the body, serotonin and norepinephrine.  A few other drugs also increase the levels of serotonin in the body.  If these effects add up, a reaction can occur.  Some other drugs that may significantly  increase serotinin levels are Prozac (fluoxetine), Anipryl (selegeline), and Elavil (amitriptyline).  You should double check with your veterinarian if your dog is on these drugs already, and you have a prescription for mirtazapine.

For more information on topics like this, check out The Dog Cancer Survival Guide.


Dr D

Leave a Comment

  1. BettyD on December 16, 2018 at 3:47 pm

    Our Rottie named Chewy (Chubaca) is eight years old in April was diagnosed with Lymphoma. Chewy started his Chop Chemo in May came out of remission. Next step to try LAP Chemo same result. Third time had Chewy try Tanovea Chemo. Chewy had bad side effects on the first treatment. Chewy would rest one week and on the second treatment would lower dose on Chemo. With Side effects Chewy started losing his hair. Stopped Chemo treatment after second treatment. Noticed part of Chewy’s back his hair gets matted and falls off. Really don’t know what to do? Not sure if his meds (prednisone, omeprazole, clopidogrel), chemo, or food (boil chicken, liver, broccoli, Nutri Source), Chewy also has arthritis in his right front leg which is taking tramadol for now.

    Chewy is taking K9 Immunity Wafers (6 a day) and just started him on Apocaps (3 a day for now).

    HELP! Need your Advice! We Love Our Chewy – He’s Smart, Kool Temper, and Handsome!

    • Dog Cancer Vet Team on December 17, 2018 at 9:15 am

      Hello Betty,

      Thanks for writing, and we’re sorry to her about Chewy.We’re not veterinarians here in customer support, so we can’t offer you medical advice. However, we can provide you with information based off Dr. Dressler’s, and Dr. Sue’s writing 🙂

      In Chapter 29 of the Dog Cancer Survival Guide (this entire chapter is dedicated to Lymphoma) Dr. Sue writes that her treatment of choice for Lymphoma is the CHOP protocol, as these combination protocols have had the best success rates (CHOP protocol usually last between 19-25 weeks). However, each dog, and their health situation is unique, so each approach needs to be tweaked.

      You aren’t alone in wondering whether to start chemo again In this situation, Dr. Sue writes that, in general, the likelihood of a second remission is 50%, and the second remission usually lasts 50% as long as the first. We highly recommend that you get a copy of the Dog Cancer Survival Guide and read what Dr. Sue has to say on Lymphoma, relapses, treatment options, and alternative chemo options.

      Consult with your vet about the side effects that your dog is experiencing–they may be able to make recommendations on how to help manage them 🙂 Dr. D also has written a great article on supplements for dog’s with cancer that you make find helpful. Here’s the link:

      As Dr. D writes in the Dog Cancer Survival Guide, there are many things that you can do to help your dog with cancer, such as conventional treatments (chemo, surgery, or radiation), diet, nutraceuticals, mind-body strategies and immune system boosters and anti-metastatics. Here’s a link to the Dog Cancer Diet PDF that readers of the blog can get for free :

      Your vet is the best person to consult with as they know your dog the best and can provide recommendations that will work alongside your dog’s current treatment plan

      We hope this helps!

  2. marina ohara on June 4, 2013 at 10:21 am

    would like to recive dog cancer news, i have a shihtuz with chronic lymphocytic leukemia she is on leukeran(chlorambucil)

    • Susan Harper on June 4, 2013 at 11:41 am

      Hi Marina, You’re all set to receive the dog cancer news. And you should find the blogs very helpful. Don’t hesitate to pour through them and absorb the info there. Have you downloaded the dog cancer diet? You can use the form at the top of this page to get it by email. The team is here to help when you need it.
      Susan / Dog Cancer Support Team

  3. Joanna on February 6, 2013 at 7:16 am

    My dog just started this med yesterday. I’m at the end if my tope trying to get him to eat the past few days. My boy Fozzie will be 15 next month. He was diagnosed with hepatocellular carcinoma in oct/2012. He also has a large necrotic mass in his abdomen. Chemo would poss cause this to rupture..and he is not a candidate for surg bc of the cancer. His quality of life is most important to me. I’m hoping this med will get him eating better so maybe he will feel better.

  4. Dr. Demian Dressler on September 28, 2012 at 12:59 pm

    Serotonin syndrome is possible but rare. it is easily reversed with stopping at least one of the meds and giving cyproheptadine. The dogs just get vocal and act weird.

  5. Sarah on September 25, 2012 at 6:15 am

    Steve – your post was quite some time ago, so I’m not sure that this is relevant anymore, but my vet clearly advised not to mix tramadol with mirtazipine for the same reason Sharlene mentioned in her post.

  6. Mj on August 23, 2012 at 4:34 pm

    My soon to be 11-year old Wheaton Terrier suffers from histiocytic sarcoma. Was starting to decline – seriously thought she’d be gone (would have to put her to sleep) within days. 5 days later after starting the mirtazapine she’s much more active and eating hamburgers and Blue Buffalo Dog bones. So far its been a life saver for her…. I know she never would’ve eaten again without the med. Currently giving 1/2 of a 15 mg. tab daily. Thinking about increasing dose to see if she’d eat even more… any comments on dosage?

    • Dr. Susan Ettinger on August 27, 2012 at 4:36 pm

      Hi MJ,
      I often use mirtazapine as appetite stimulant, and I cannot make recommendations for a dog I have not examined. With that said, I would not recommend giving more than 1/2 a tab to a Wheaton, but best to discuss directly with your vet.
      All my best, Dr Sue

  7. steve on August 18, 2012 at 11:39 am

    I would like to hear Dr.D’s thoughts on the last comment by Sharlene.
    My dog was prescribed mirtazipine and tramadol together after he had a abdominal exploratory surgery which revealed a tumor in his small intestine and some metastasis. Is it true that these drugs together can cause Serotonin Syndrome .
    I am interested to hear where Sharlene’s information is coming from and if she is correct

  8. Sharlene on August 14, 2012 at 6:00 pm

    Do not use this medication if your dog is taking Tramadol for pain due to cancer. It can cause Serotonin Syndrome.

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