Reader Question about Osteosarcoma in Dogs Treatment Options
Albert wrote to us asked about his 65 lb Doberman, who had just been through an amputation to remove osteosarcoma in her right front shoulder. Since the cancer is in the lungs already, he wants to try his dog on ivermectin and fenbendazole. This article serves as information about the sources for those medications, the doses I recommend as a veterinarian, and a protocol that Albert can use.
Important Veterinary Disclaimer
This article is for informational purposes only and is not a substitute for veterinary diagnosis, oncology care, or treatment advice for your own dog. Please note that ivermectin and fenbendazole are not approved cancer treatments for dogs. They should only be considered with veterinary guidance, especially in dogs with cancer, liver disease, neurologic signs, other medications, or possible MDR1 drug sensitivity.
Can Ivermectin and Fenbendazole Treat Cancer?
Ivermectin and fenbendazole have both been shown to work in the laboratory against cancer cells, but are not approved for use in treating cancer in dogs.
No veterinarian can guarantee them, but then again, no one can say this is a dangerous treatment to deal with this fatal disease. Most of this information on the use of these medicines is anecdotal, just success stories from people who have tried these alternatives when their dog had cancer.
Where to Buy Ivermectin
The best form of ivermectin I have found for most dogs is the ivermectin sheep drench.
This is the Amazon link for ivermectin, but you can also buy it at feed stores and pharmacies that sell medications for livestock.
The reason I like this form is that it is relatively palatable, as most dogs do not like the taste of ivermectin in the other formulations.
Ivermectin Dose for Dogs
This is the dose most commonly used.
| Body Weight (lbs) | Body Weight (kg) | Dose (mcg) | Sheep Drench (ml) |
|---|---|---|---|
| 5 | 2.3 | 460 | 0.6 |
| 10 | 4.5 | 900 | 1.1 |
| 20 | 9 | 1,800 | 2.3 |
| 25 | 11 | 2,200 | 2.8 |
| 30 | 14 | 2,800 | 3.5 |
| 35 | 16 | 3,200 | 4 |
| 40 | 18 | 3,600 | 4.5 |
| 45 | 20 | 4,100 | 5 |
| 50 | 23 | 4,600 | 5.8 |
| 75 | 34 | 6,800 | 8.5 |
| 100 | 45 | 9,000 | 11 |
For your dog, she should receive 7.5 cc once daily, so that bottle from Amazon will last about four months.
You can use the cattle form if the cost is too much and can disguise the taste by putting it on a biscuit or small piece of bread.
Never use the horse paste. The concentration is higher, and even though the toxic dose of ivermectin is quite high, dogs are more likely to be overdosed.
How Often Should I Give My Dog Ivermectin?
Ivermectin has been used every day for at least two months in dogs with generalized demodectic mange, so we know that it can be used safely every day for at least that long.
Since your dog has been diagnosed with osteosarcoma, I would recommend it be given daily. For a less aggressive type of cancer, I suggest only every other day so the medicine does not build up to dangerous levels.
Watch for excessive drooling, dilated pupils, and a wobbly gait or even falling over.
If she is doing okay three months after starting the therapy, it is a good idea to give her a 15-day rest before resuming the therapy.
If you are combining this with fenbendazole, there have been no reports of the drugs interfering with each other, so they can be given on the same day.
Will Fenbendazole Also Help With the Cancer?
The dewormer fenbendazole kills cancer cells by disrupting the function of the cancer cell microtubules.
It may not be as effective as ivermectin, and there are some liver toxicity issues, but since it attacks the cancer in a different way than ivermectin, it may help.
The dose is still controversial, as the only suggestions have been to use the dewormer dose, which is about 50 milligrams a day per kilogram of the dog’s weight for three days.
You can do this for 60 days and monitor the response. You can buy this at your local feed store or pet shop, and if you have questions about the dose, leave a comment with the strength you have purchased and your dog’s weight, and I will get back to you.
No one can promise you that this medication will not cause toxicity, but this protocol does work in some dogs and it may extend the pet’s life.
Where to Buy Fenbendazole
Here is a link to fenbendazole if you want to get it from Amazon:
Link to purchase fenbendazole on Amazon.
Give 10 cc each morning, or 10 ml, either in her mouth or on a dog biscuit or whatever she likes to eat. Use it for three days, give her four days off, then give it for another three days.
That bottle I linked to here is equal to about 10 doses.
If you do not use Amazon, you can buy it at farm stores and most pet shops. It is also available as a powder.
In most cancers, it is recommended to give this for a 60-day cycle, but osteosarcoma is so aggressive that there is no reason to stop unless she is having diarrhea, vomiting, or any other negative signs.
My Opinion on Osteosarcoma in Dogs Treatment Options
There is no guarantee that ivermectin and fenbendazole are going to extend her lifespan since she has been diagnosed with osteosarcoma.
One other thing you can do that might help, however, is to switch her to a ketogenic diet.
A dog’s tumor cells require glucose to thrive, and cutting off their food source means that they cannot grow as fast. The other cells in her body will do just fine on ketones, but tumor cells will not.
You can see my video on the ketogenic diet here:
There are plenty of great recipes out there, but this has to be homemade. Do not buy one of the commercial diets that claim to help.
Albert, thank you for reaching out to us with your question. If you have any other questions or updates on how your Dobie is doing, you can contact our team here at YourPetsAtHome.com. Wishing you all the best.
References
- Hulscher N, Victory K, Thorp JA, Pinsky D, Diaz-Villalobos A, Gillooly P, Coulson F, Annazone M, Radesi C, Brooks J, McCullough PA, Risch H. Real-world clinical outcomes of ivermectin and mebendazole in cancer patients: Results from a prospective observational cohort. Anticancer Research. 2026 Jun;46(6):3243–3255. doi:10.21873/anticanres.18194. PMID: 42203321.
https://pubmed.ncbi.nlm.nih.gov/42203321/ - Diao H, Cheng N, Zhao Y, Xu H, Dong H, Thamm DH, Zhang D, Lin D. Ivermectin inhibits canine mammary tumor growth by regulating cell cycle progression and WNT signaling. BMC Veterinary Research. 2019 Aug 2;15(1):276. doi:10.1186/s12917-019-2026-2. PMID: 31375107; PMCID: PMC6679554.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6679554/
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