Vicki writes to Dr. Mark regarding advice for her dog’s soft tissue sarcoma treatment and dosing instructions using Ivermectin and Fenbendazole. Initially, her dog’s tumor was surgically removed, however it subsequently returned and is now larger than it was before the surgery. Dr. Mark offers the following treatment advice for her to discuss with her vet, as well as dosing information for readers to discuss with their veterinary professionals. This is a protocol with which he sees success.
Reader Question: Dog Soft Tissue Sarcoma Treatment Options and Dosing
We have a 23-pound, 8-year-old male Jack Russell with a grade 3 soft tissue sarcoma on his front leg. Initially, it was surgically removed March 24, 2026. Since then, it has returned at the same location and is larger than before. I am going to start the Ivermectin and Fenbendazole regimen, but I need to know the dosing! I purchased the pill form of Ivermectin (6 mg pills) and Fenbendazole pills at 223 mg per pill.
Also, is there is an ointment that would help with the inflammation. I’m afraid that it’s going to pop open. I’ve been giving turkey tail mushroom daily, and he is also on prednisone 5 mg daily per his vet.
Dosing Instructions Ivermectin for Soft Tissue Sarcoma in Dogs
The correct dose of Ivermectin for a dog of your size is about 2000 micrograms. As one-half of the tablets you have is 3000 micrograms, it is naturally difficult to split them and get an accurate dose. I suspect the pills you have are labeled for humans.
With smaller dogs, I prefer to use the sheep drench Ivermectin since it is 0.8 percent and easy to get an accurate dose, even with dogs much smaller than your Jack Russell Terrier. This is the brand I usually use: Durvet Ivermectin Sheep Drench
If you cannot get that at Amazon or a local feed store, you will probably be fine with giving the slightly higher dose, since Ivermectin is quite a safe drug (I am referring to the half pill with a little bit shaved off of it). I cannot guarantee that will be ideal, which is why I would prefer that you use the sheep drench. The sheep drench is also more palatable; however, if you use the pill form, you can put it in a treat like cheese, and then that will not be an issue.
Please be aware of the signs of Ivermectin toxicity. If he starts vomiting or has other GI signs, you should stop this treatment. However, veterinarians have treated dogs with higher doses of ivermectin for demodectic mange for several months without problems.
Note: Ivermectin should not be used on dogs with the MDR1 gene (herding breeds are most commonly affected).
Common Signs of Ivermectin Overdose
- Nervous system: Trouble walking, shaking, tremors, seizures, and confusion.
- Stomach and mouth: Heavy drooling, throwing up, and not wanting to eat.
- Eyes and face: Large pupils and sudden blindness.
- General body: Extreme weakness, slow heart rate, deep sleep, or coma
Ivermectin Dose for Dogs
Below are the doses most commonly used by weight.
| 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 |
Fenbendazole Dosing Schedule for Soft Tissue Sarcoma in Dogs
As far as the Fenbendazole goes, the correct dose is the one used for deworming, which is 23 mg for each pound of body weight. Specifically for your dog’s weight, give him two pills a day for three days, then give him four days off. Repeat the cycle of three days on and four days off, for a total full cycle of 60 days. This 60-day cycle of three days on and four days off works for dogs of all sizes.
Topical and Pain Treatments for a Growing Sarcoma Lesion
Regarding the lesion itself, is it open now? If so, I do not recommend that you use an antibiotic cream, even though the prednisone can make the sarcoma itself more likely to become infected. Therefore, I suggest these alternatives to an antibiotic cream:
- Initially, use coconut oil as a moisturizer if it is breaking open from being too dry.
- However, if the leg seems painful, look into CBD oil, which is most likely to help with pain and moisturizing the skin over the lesion.
- Additionally, your veterinarian may prescribe an NSAID like Rimadyl for the pain.
Keep up the turkey tail mushroom treatment! If you have any other questions during his treatment, please contact our team. We are all hoping things go well for him.
Further Reading for Dog Soft Tissue Sarcoma Treatment with Ivermectin
Hu B, Tan H, Yu L, Liao Q, Guo W. Repurposing Ivermectin to augment chemotherapy’s efficacy in osteosarcoma. Hum Exp Toxicol. 2022 Jan-Dec;41:9603271221143693. doi: 10.1177/09603271221143693. PMID: 36503300.
Tantawy R, Raafat SN, El-Gawish A, Ghalwash D. Synergistic potential of Ivermectin and doxorubicin in oral squamous cell carcinoma: an in vitro investigation. BMC Pharmacol Toxicol. 2025 Dec 12;27(1):16. doi: 10.1186/s40360-025-01053-4. PMID: 41382246; PMCID: PMC12817848.
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 Vet Res. 2019 Aug 2;15(1):276. doi: 10.1186/s12917-019-2026-2. PMID: 31375107; PMCID: PMC6679554.
