How Much Fenbendazole Can I Safely Give My Dog?

Fenbendazole, how much? We get a lot of emails from people asking this question; it is the question asked most. Nothing is more heartbreaking than finding out your best friend in the world has cancer.  When we found out that Simon had cancer, my heart sank.

The last thing I wanted to do was something that would harm Simon. It’s the very reason we opted to not give him chemo. I have known many people killed by the very drug that was designed to save them, it’s that toxic. When asked, if chemo will cure the cancer, the stock answer is no, but it might buy you some more time. This is the answer we were given when Simon was diagnosed, and it was not the answer I wanted to hear.

So, to answer the question. First, I am not a veterinarian and I can not give anyone medical advice as to the treatment of their pet. I can tell you what worked for Simon as well as share information from others as to the efficacy and safety of Fenbendazole.

The Dose We Gave Simon

Simon weighed 90 pounds and was given 250 mg of Fenbendazole twice daily for over four months. A full worming dose of Fenbendazole for a dog weighing 90 pounds is about 2000 mg per day for 4 days, which is 4 times the amount he was given to treat the cancer. 

About 3½ months into his treatment we did a full blood panel on him and it came back with no evidence of toxicity. What we gave him worked. Fenbendazole is not easily absorbed and about half of it leaves the body in feces. It is very important to give vitamin E as well as some fat at the time you dose Fenbendazole to aid in absorption. Vitamin E Succinate is recommended.

Dosage Used By Others

We received an email from someone who was working with their vet in administering Fenbendazole. They have a small dog that is just under 10 pounds and is in the late stages of cancer. Their vet recommended the full worming dose daily, with no breaks.

Another person posted their treatment protocol on the Facebook group “MY Cancer Story Rocks for Pets”. They had a dog weighing about 40 pounds and their vet recommended a dose of 33% of the worming dose daily. Joe Tippens, the man from whom we got the idea to treat Simon with the Fenbendazole, took 222mg of Fenbendazole daily and he weighed about 150 pounds when he started his protocol. As you can see, the amounts of Fenbendazole vary greatly.

How Safe Is Fenbendazole?

If you do a little research, you will find it is very safe. To give you a general idea, I am sharing a link to a blog at Cornell University. Here is a quote from the blog:

“Fenbendazole, the active ingredient in Panacur and Safe-Guard, is a benzimidazole dewormer which prevents cell division. It is generally considered a safe drug, with toxicity only occurring at 100x overdoses and in exotic species. Fenbendazole isn’t systemically absorbed and over 50% leaves the animal in feces. It must be given for at least 3 days to kill parasites since it needs to halt cell division for a certain duration before it is fatal to the parasite.” Here is the link to the blog:

There is information regarding the toxicity of Fenbendazole within the Vitamin E Succinate white paper on our site. It concerns the LD50 (Lethal Dose in 50% of test subjects) of Fenbendazole. It states an LD50 in mice of 10,000 mg per kg. To put that into perspective, Simon’s full daily dose of Fenbendazole was 500 mg is the equivalent of 12.24 mg per kg, which is a long way off from 10,000.

I realize that LD50s are different in different species. I am just demonstrating the safety. Some breeds of dogs are sensitive to Fenbendazole so consult your veterinarian before giving your dog Fenbendazole.

So, What Is The Correct Dose?

The correct dose is the one that is working for your pet. What I am trying to say is not to put your emphasis on worrying about hurting your pet by giving them too much Fenbendazole as long as you stay at the recommended worming dose or less. It appears that Fenbendazole is very effective in treating cancer and that large doses may not be needed, but they are safe over extended periods of time. Out of the doses I read about, I liked the recommendation of 33% of the full worming dose.

Please check with your vet. See the final update here: All Dogs Go to Heaven