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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


Discover the Full Spectrum Approach to Dog Cancer

Leave a Comment





  1. Deborah on June 19, 2020 at 4:08 pm

    Thank you for this information, my 20 year old chi has lymphoma in her neck. I will be asking our vet about doxycycline for her. We want to help her. She is our child. Her name is Princess Diana.

  2. Justine Freeman on March 20, 2019 at 3:21 am

    Can Doxy be used in conjunction with Apocaps?

  3. Ann Shonert on March 13, 2019 at 5:36 am

    I have a Boston Terrier with 3 or 4 cancerous lesions…diagnosed by aspiration by a vet in August. I was told he’d have maybe 3 months to live. They gave me 5mg Prednisone & I myself started him on a half benedryl daily.
    3 months later read about doxy. G began giving him a dose daily. I know it’s not good to self treat. But, the vet refused to do anything else. This is a well know full surgical vet hospital in MO. Putter…the Boston is doing fine. Lessions have grown a little. I’m scared to death of losing him. I just don’t know if my dosage is exact & for how long I should use doxy,??

    • Dog Cancer Vet Team on March 13, 2019 at 6:30 am

      Hi Ann,

      Thanks for writing, and we’re sorry to hear about your boy. As we’re not veterinarians here in customer support, we can’t offer you medical advice. However, we can provide you with information based off Dr. D’s writings 🙂

      On pages 192-193 of the Dog Cancer Survival Guide, Dr. D provides more information on doxycycline including the precautions and dosage 🙂

  4. Lisa kalis on February 5, 2019 at 9:02 am

    Can a dog with diabetes AND cancer take the antibiotic doxycycline my rottie is 9 on supplements wondering if this will do any good?

    • Molly Jacobson on February 5, 2019 at 9:58 am

      Hi Lisa, check with your veterinarian about whether doxycycline will affect your pup’s diabetes. I’m not sure whether it affects blood sugar levels, but your vet will be able to find out. Plus, you need to get the med from your veterinarian anyway — so ask when you bring this up in your next visit. Thanks!

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