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

An Antibiotic for Dog Cancer

Updated: March 20th, 2019

Antibiotics are normally used to treat infections, but not many know that there are anti-tumor antibiotics.

One of the cheapest, safest, and most easily obtained through a vet? Doxycycline.  Now, doxycycline is not a dream antibiotic.  It actually has fairly limited use as an antibiotic.  Some use it for dental infections, but it is most commonly used to treat certain blood parasites.

Some exciting news about doxy?  It has anticancer effects!

Doxycyline helps suppress angiogenesis (new blood vessel formation that feeds tumors and robs the body). In this way it slows tumor growth. It blocks enzymes called matrix metalloproteinases (MMP’s) that digest the tissue around tumors, allowing new blood vessels to be formed. Check it out here.

Not having access to as much blood supply, the cancer cells are less able to metastasize through the circulation.  This lessens the spread of some cancers. Read more.



In the lab, this drug can induce apoptosis (normal, healthy, programmed death) of cancer cells.  This is a direct action on the cancer cells, and may have some usefulness in cancers like lymphosarcoma. Here’s the abstract.

In humans, this drug has been a disappointment for cancer treatment.  But in dogs, according to Greg Oglivie, MMP inhibitors (of which doxy is one) combined with chemo for lymphosarcoma improved survival times in some older dogs in double blind, placebo-controlled clinical trials.

Although this is a prescription drug, it is widely available and inexpensive.  It can be used with most other agents used in fighting cancer, and is quite safe.

When young dogs take doxycycline, some may develop yellowed teeth. It may cause abnormalities in the cartilage of developing pups in the uterus, so do not give it to pregnant dogs.  It should not be given with calcium-containing foods as this may lessen absorption of the drug.

Best to all,

Dr D


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  1. Our Baby on April 3, 2014 at 2:33 pm

    The Vet says our 15 yr old Cocker has a malignant tumor in her mouth on her gum. Recommended surgery, chemo and radiation. We said NO. We started her on our own protocol of “DCA, Turmeric and Baking Soda” once daily wrapped up in her favorite deli ham. The tumor has shrunk by 1/2 in 3 weeks!! We are ecstatic!! Her over all health signs are improving as well.

    • kimber's mom on May 10, 2014 at 9:38 pm

      What is DCA?

  2. Ann on March 2, 2013 at 5:10 pm

    Our beautful girl, Ollie, a 10 year old golden retriever, has been diagnosed with cancer.

    Timeline
    Early fall 2012- She starts vomitting right after eating. Vet suggest 2 pepcid in with food. Vomitting stops.
    Mid Nov. 2012- We first notice a “lump” in her neck.
    Dec. 31, 2013-We take go to the vet. Needle asperation. Vet says it’s probably lymphoma. We wait for results.
    4 days later- Vet calls can’t believe it’s not lymphoma. Maybe tick borne disease. Starts doxycycline 2 pills twice a day. We give it to her. she vomits. We space out the pills and give them every 3 hours. 8am, 11am, 5pm, 8pm
    2 weeks later we return to the vet. No change in glands. He explains we aren’t giving the dose right. We get 2 more weeks of pills and give them correctly. 2 at 8am, 2 at 6pm. After about 10 day lymphnodes shrink alittle.
    Then grow back bigger.
    return to the vet more glands now involved shoulder and groin area.
    We go to specialist, oncologist, Recommendation Have a gland completely removed, tested in California.
    Feb-19 She has surgery and is prescribed antibiotics.
    Feb. 26 results/diagnosis-low grade small cell lymphoma t-zone type.
    Feb. 28-We go back for node measurement becuase she is acting sluggish.
    The vet examines her groin area and notices an area of concern that she (nor the other 4 vets) had not felt before. She asperates it.
    She sees (a couple irregular cells). She nows has Ollie has either Histiocytic sarcoma, Hemangiosarcoma, or Soft Tissue sarcoma. The next step would be more surgery, test, x-rays, mri’s. etc. In the end the area is in a place that would likely require amputating her rear leg. (We aren’t doing that)
    We gave the last antibiotic pill yesterday.
    Today, the huge glands in neck neck are either gone or have shrunk 75%.

    So my question is should we start doxycyline. My though being the restriction of blood supply to these areas.

    Thank you

    • Dr. Demian Dressler on March 6, 2013 at 4:16 pm

      Dear Ann
      I am sorry you and your dog are going through this. Goldens are now the number one dog that get dog cancer, with about 75% of them getting the disease. So your dog may indeed have two cancer types. As to whether we have tick borne blood parasitism, there are tests for that which should be done to rule them in or out. Discuss starting doxy again with your vet as it may have caused vomiting…you could give it with a full meal and also use some mirtazapine or metoclopramide along with it to help with nausea. Again, touch base with your vet. Have you read the Guide so you are aware of all the options you have?
      https://www.dogcancerblog.com/blog/an-overview-of-what-else-can-i-do/
      I hope this helps
      Dr D

  3. Mark on January 4, 2013 at 7:44 pm

    Hi Doctor Dressler..
    My 11yr old boxercross had a phantom pregnancy, lactating etc 3mths ago…then had a little lump form in one of her rear glands..BBsize,
    The vet prescribed cephalexan 500mg and after only 7 days the lump grew to the size of a golfball which then was diagnosed as a malignant tumor,
    (It does make me wonder whether certain meds feed the tumor or fight them..?)
    She had surgery,3 of the chain removered and seemed to recover well..
    Unfortunately..a month later the tumor returned and another formed on the other rear remaining breast.
    Her lymph nodes under her arms are swollen and she has fluid building up on her underbelly/chest and rear legs have swollen.
    Today i visited the surgeon and he prescribed Prednisone 20mg..thinking surgery just delaying the inevitable..
    Any suggestions how to prelong her life as shes still very active would be much appreciated..?
    (also would the navy protocol help in anyway?)

    • Dr. Demian Dressler on January 29, 2013 at 5:52 pm

      Dear Mark,
      was your dog spayed? This can help decrease some cases of mammary cancer regrowth. Also I would be thinking of the other steps in the Guide- diet, apoptogens, immune support, and so on. The chemo options are a bit limited with most mammary cancers I am sorry to say.
      Maybe this will help:
      https://www.dogcancerblog.com/blog/an-overview-of-what-else-can-i-do/
      Best
      Dr D

  4. Vadym on June 19, 2012 at 7:23 am

    Dr. Dressler:
    We have a dachshund, 13 years.
    2.5 years ago she had a surgery and mammary glands 4 and 5 were removed from each side.
    Biopsy showed a cancer. She was ok until this February when it came back.
    It looks horrible, whole belly is like pomegranate and it is bleeding and spreading.
    She always was on protein diet , only raw meat.
    Now she is taking meat , spinach, garlic, broccoli and fish oil, echinacea, propolis.
    Would Doxycycline be helpfull for her to slow down the process?
    Thank you.

  5. mike on June 14, 2012 at 3:38 pm

    Hello doc,

    I recently got the bad news that my 11 year old german shepard had an anal sac tumor. We had the tumor taken out last week, she is recovering fairly quickly. Our vet just called yesterday to tell us the tumor test results came pretty much as expected-anal sac andeocarcinoma. We can’t afford chemo nor do I want to put her through any more stressful vet trips….any prescription/natural meds you can recommend would be greatly appreciated. Baytril? Pre-surgery I would have never even known she had any problems what so ever. Extremely playful and never stops running and enjoying life! Post surgery she almost can sense I know this is very threatening.

    Thanks for any response.

  6. Roland on May 9, 2012 at 4:06 pm

    Hi Dr D my 9 year old collie X has been diagnosed with osteocarcinoma in the skull. I have decided against surgery and Chemo as cost is prohibitive and benefits are uncertain. He is now on a cancer diet and I have ordered Artemix. I am wondering if Doxy and Artemix could be combined?

  7. Austine on February 7, 2012 at 6:12 am

    10.5 y/o Labrador/terrier has Mct. Can the doxycycline help her?

  8. Julius Moultrie III on December 20, 2011 at 7:51 am

    Dr. Dressler:

    My 4.5 year old French Mastiff was diagnosed 1 week ago with canine lymphoma with a tumor in his chest, abodomen, and 2 under his mouth. Currently we are give him 2 Prednisone pills a day, 1morning/1evening. He has a great appetite and loves the his high calorie meals with 1tbls of flax seed oil that he gets. We are waiting for the K9 Immunity Plus with Transfer factor to be delivered so we can include it with his present treatment. Should we also start giving him Apocaps as well?

    • Dr. Demian Dressler on December 21, 2011 at 8:42 am

      Dear Julius,
      I assume conventional chemo has been thoroughly evaluated? This is one of the most treatable cancers with chemo.
      If you are relying on Prednisolone only, the life extension is usually only a couple of months.
      Apocaps with pred can be done, but needs to be monitored very closely by your vet. I worry about digestive upset (vomiting, diarhea, loss of appeitite) if the pred dose is high (can’t tell based on comments) or if your pooch has a sensitive stomach.
      Talk with your vet about using Apocaps on days off pred or at 1/4 the labeled dose with food.
      Flax oil is has much less beneficial effect than krill or fish oil, as you will read in the Guide, which I always recommend.
      Best
      D

  9. Angie Jones on November 9, 2010 at 4:57 pm

    Dr. Dressler,
    My beagle, Gordon, is just coming out of remission of his lymphoma. He started a rescue protocol (Madison-Wisconsin) yesterday. I asked our vet if he was familiar with LDN which he wasn’t but he is familiar with the doxycycline studies.

    He is supportive of our interest in trying it but not sure what the dosage is for our 42 pound beagle. Can you help?

    Thanks,
    Angie

  10. vapor cannon on June 30, 2009 at 4:04 am

    its nice to know that Doxycycline can be used to fight cancer to human and even in dogs. Thank you for sharing this article.

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