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Cimetidine’s Anti-Cancer Effects in Dogs

Recently, Tripawds member Tai brought Cimetidine’s anti-cancer effects to our attention. This is an over-the-counter heartburn medication for humans (also known as Tagamet), has been found to prevent  reduce the risk of cancer metastasis in dogs with mast cell tumors. Several reputable studies have reported this positive news about Cimetidine anti-cancer properties.

Please see 2021 update below

How does Cimetidine (Tagamet) help treat Mast Cell Cancer in Dogs?

cimetidineCimetidine is often given to Tripawds to help with nausea after chemotherapy.  Or, to prevent gastric ulcers when switching medications, such as NSAIDs. Has your vet has prescribed an acid-reducer to help with nausea, such as Prilosec? If so, ask if it’s OK to give Tagamet instead. According to Cimetidine is the generic form of the brand name drug Tagamet.

Cimetidine is often used to treat and prevent ulcer formations in the pet’s intestine and stomach. It works to adjust the pH balance in the stomach by blocking the histamine-2 receptor.

Cimetidine is also known as histamine a2 antagonist, as it reduces acid formation in the stomach. Although it may not be beneficial to pets with high grade cancer, it can help to reduce the effects of mast cells on the gastrointestinal tract.

Dr. Demian Dressler, author of the Dog Cancer Survival Guide, has also added Cimetidne to his list of possible mast cell tumor treatments, and Tai posted information about several studies which discuss this drug’s anti-cancer effects. Another study by Life Extension Foundation, says:

“Cimetidine works through several mechanisms of action, preventing immune suppression caused by tumor secretion of histamine, halting cancer growth, preventing angiogenesis, promoting cancer cell death, and averting often-fatal cancer metastasis.”

Cimetidine is also known by the brand names of  Tagamet, and is in the same family of drugs as Famitidine, Ranitidine and Zantac. Ask your vet for details about whether it’s right for your Tripawd.

*2021 Update on Tagamet and Benadryl to Treat Mast Cell Cancer

Science is always changing, so if you are considering using Tagamet to “cure” mast cell cancer, please check out this important discussion with Dr. Nancy Reese, DVM, PhD, on The Dog Cancer Answers podcast, “Do Tagamet and Benadryl Cure Cancer?.” 

Despite these benefits, Tagamet and Benadryl are not a miracle cure for cancer.

Dr. Nancy says, “If there was something that was easy, like Tagamet and Benadryl, that would cure cancer, I would buy stock in Benadryl and Tagamet!”

Dr. Nancy cautions owners about believing therapies that sound too good to be true.

And definitely don’t delay treatments that are scientifically and clinically proven to help fight and even reduce cancer in order to chase after a fad protocol.  — Read more on The Dog Cancer Blog


32 thoughts on “Cimetidine’s Anti-Cancer Effects in Dogs”

  1. My dog has prostate and bladder cancer. Is there any evidence Cimetidine is effective on slowing this form of cancer?

  2. I read about this about 4-5 months months ago. Very interesting…Charley has been taken generic pepcid (famotidine) 2x/day the past 2 years because he was a puker. If it’s an added bonus to cancer that’s even better news!
    Ellen & Charley

  3. 2 of my boxers recently were diagnosed with mast cell tumors. Neither tumor was operable (one inside the ear of my 12 year old dog who was having seizures, the other the entire upper eyelid of my 13 year old boxer). Both were started on diphenhydramine at 4 mg/kg, twice daily; cimetidine 4 mg/kg, three times daily. My 12 year old female, Gretakins, was immediately started on oral prednisone at 2 mg/kg, twice daily. In 14 days her visible tumor was gone, as were her vomiting, diarrhea, seizures, and neurological issues (seizures, high stepping, decreased eyesight). My 13 yr old’s (King Gustav) eyelid returned to normal size within 7 days. Mast cell tumors were confirmed in both via fine needle aspirate. We went through a LOT of puppy pads, but both my babies are clear and healthy today. Gretakins is 1 yr out (she wasn’t expected to survive 30 days from diagnosis date). King Gustav is 6 months out from treatment start date. I’m a veterinary technician, and am overjoyed that my rescue babies have done so well after such a sad diagnosis.

  4. @Helen Martyszyn My heart goes out to you. My girl had mast cell cancer and I had her on benadryl and tagamet for 15 months and she did great. She ended up getting hemangiosarcoma last summer and quickly declined, leaving me 4th of July 2016. 🙁 Prayers to your doggie. Miracles can happen.

  5. My Sweet Cherry Pie has nasal cancer. She was deemed non operable due to the size of the tumor that grew in her mouth, post punch biopsy at that spot.
    We opted out of radiation and chemo.
    At the 2 1/2 week point of being on Tagamet/Benadryl protocol, she appeared to deteriorate. She didn’t act well, her muzzle became swollen. Then she’s started back up with the sneezing, which caused her to have nose bleeds.
    Fortunately I was prepared with Yunnan Biayso (Chinese Herb to stop/prevent bleeding). I was able to keep her bleeding pretty much under control. It lasted several days. During that time she looked miserable!! Her inner eyelids wouldn’t open and she kept having bleeds.
    After a sneezing attack I found a tumor the size of a medium blueberry and two additional pieces of tissue. I later found an additional shriveled up tumor I missed when I was vacuuming.
    I was concerned when she looked so badly. But I knew the treatment could cause the tumors to swell and hopefully die off. Fortunately with nasal cancer there is a greater chance of the tumors being sneezed or wretched out.
    After a few days the bleeding stopped and she began to feel better.
    Then here came the snot!!
    She developed a secondary nasal infection. Which, again, I was prepared for with antibiotics on hand.
    Sneezing is the way a dog will blow their nose.
    I had taught her (or as usual she actually figured it out and taught herself) to sneeze on command. So after the threat of dislodging a crucial blood clot, I’d take her outside to “Sneeze Cherry, sneeze!”.
    Keeps the snot outside and clears her sinuses.
    One and a half weeks after the initial episode, she was back to her old self. Playing fetch, correcting the puppy and just being Cherry!!
    I did find out after the fact that at the 3 week period of Tagamet, the tumor will start to bleed as it dyes (?). So if your dog has internal tumors the bleeding if left unchecked could be problematic (as in liver cancer). So be prepared and start them on the YB for bleeding in advance!! Don’t wait until you think your dog is bleeding.
    Just know that your dog may have a bad spell. But stay the course.
    Sorry this is so long. I just want to help people and their dogs out.
    I gotta go and throw the ball in the backyard for Cherry!!

  6. I’m having doubts about this treatment as I haven’t seen results for my dog although I see many success stories . The lady I know who promotes this on Facebook blocked me rudely after questioning it, she did claim I mixed other supplements. Told me to stop Yunnan Baiyao etc . No tumeric no fish oil , the problem is oils are in a lot of foods for dogs even the nutrical I was giving him to help him gain weight … he skin and bones. Can anyone speak to this ? Does this really work provided no fish oils .. no other supplements? Thank you

    • Laurel, follow your gut. Your pup needs you to find a proven, science-based way to help him. As far as I know, this treatment is not widely used and there is probably a good reason for that. Consult with a veterinarian expert as soon as you can so you can get your pup eating again.

  7. My dog has an angry mast cell tumor and it also spread to her spleen :(. I have been giving her Pepcid but after reading on a FB page Tagamet works better I changed her this week. On that page they said she shouldn’t take Tagamet longer than 7-10 days every 2-3 months. Does anyone know exactly why? I didn’t get an answer from them yet.
    She is also on prednisone, Benadryl and gabapentin.

    • Eileen, we are sorry to hear about your dog’s condition, it’s clear you are doing all you can to help her. While we don’t have an answer to your question about Tagamet, we know that your oncologist will have much better insight on it than we or any Facebook group can provide. Please check in and ask your vet for the best results. Best wishes to you both, we hope you have many happy memories together.

  8. My abbey was diagnosed with inoperable nasal tumor. Does the Tagamet/Benadryl help with nasal tumors? I don’t want to put her through radiation and I feel it would be too much on her. The oncologist that saw her only put her on an NSAID. Then I came upon this treatment that a lot of people recommended to me. Can someone help? I feel helpless and heartbroken

    • Hello Amy, I’m really sorry to hear about your pup. Please don’t follow any treatment plans you see on the internet without discussing them with a veterinarian. You could be wasting precious time and doing more harm than good. Right now your best bet is to work with an oncologist who also practices complementary medicine (i.e., ‘holistic’). They would be able to giv you more options, hopefully. Try searching the AHVMF vet directory for a provider. Also, newer types of radiation therapy (aka Cyberknife or Stereotactic Radiation Therapy) deliver a much, much smaller dose of radiation in a fraction of the time of traditional radiation therapy. That could also be an option for you. Please research that to see if your dog is a good candidate. I hope with all my heart you find a way to help your girl as quickly as possible. Best wishes and lots of love to you both.

  9. My 13 yo lab/golden retriever had her 1st MCT removed back in March and about 6 months later had 2 more pop up. The first one was grade 1, she was on Benadryl and Pepcid 2x a day. This past week we started the Tagamet and trust me I was skeptical at first but on the 3rd day of the protocol her tumor opened up and started draining. As the cancer cells start to die and shed the draining starts, it looks as if the tumor is getting eaten. She is much more comfortable and not in pain. She was also prescribed yunnan baiyao but I was also advised this will stop or slow down the draining so I plan to add the YB after doing the protocol for 10 days. It actually does work. I did get the ok from her primary vet to switch from Pepcid to tagamet. Also gabapentin and turmeric are not recommended while doing the Tagamet due to both being blood thinners.

  10. Janet, that’s pretty cool. The fact that your vet has given you the OK is wonderful, what a team effort! We are happy that your pup is doing so much better. Thanks for sharing.

  11. My 12.7 yr old pit mix was diagnosed 2 weeks ago with widespread mast cell, meaning there are tumors all over her body. Some have never moved or grown which was good, but after the vet asperated several of them (we asked her to only do one) they all became inflamed and started growing rapidly and MORE started to crop up. All she prescribed was prednisone and told me she’d need to be PTS in 3 weeks. Well, it’s been two weeks and she is still holding her own. We started on the tagamet and benadryl combo yesterday. Wish us luck.

  12. So difficult to decide. Dog had scrotum removed with good margins but was aggressive MCT. Enlarged lymph node had MCT cytology. Ultrasound of abdomen scheduled.
    1. should we aspirate spleen and liver?
    2. can Palladia, Benadryl and Tagamet be given in conjunction or should I just do the Benadryl/Tagamet and follow up with another ultrasound?
    3. Dosage 1 Benadryl and 1 Tagamet 3x daily?

  13. I have read a bit on why Tagamet is used to fight cancer but I am unclear on why the benadryl is part of the protocol. Can any one shed some light on this for me just like to understand the mechanism. Thank you

    • Wendy, that’s a great question for your veterinary oncologist. As far as we understand, Benadryl is an anti-histamine that can be helpful to control cancers like Mast Cell tumors.

  14. Hi Helmut has a large sarcoma on his scapula bigger than a melon and 2 small lung tumors. He has been doing fine. We are doing radiation to try and stop the progress of the sarcoma tumor. As far as the lung tumor s our oncologist has provided no option. We started protocol tomorrow will be 2 wks. He has started having bouts of heavy breathing. Has anyone had any experience with lung tumors. Is it common to get worse before getting better. I am scared to be making the wrong choices. I had been doing the fenbenzadole for 3 weeks but then switched to tagamet protocol. Any thoughts are appreciated. Thank you

  15. My girl was diagnosed with a nerve sheath tumour in her spinal cord in early July. They don’t know weather it’s cancer or diseased tissue that is spreading. It’s such a rare tumour/lesion that they don’t really know what it is. She is slowly loosing the use of her left forelimb now. I’ve been looking into everything that could help her but there’s not much research out there. I looked into the Tagamet and Benadryl and to be honest I’m not convinced. My specialist had never heard of it. We are going the holistic but with oncology route if they think it will help her.


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