Fenbendazole side effects seem to be generally mild in both humans and animals. While the medication was created for a primary use as a dewormer in animals, it is now being researched as a potential cancer treatment option for humans. Research is currently limited, but the studies available have shown that fenbendazole is generally very well tolerated with human consumption, and it is being actively used as part of the Joe Tippens Protocol.
What is Fenbendazole?

Fenbendazole is a benzimidazole, a class of microtubule-destabilizing agents. Other benzimidazoles, including albendazole, parbendazole, mebendazole and flubendazole have already been shown to have promising results in humans. While there have been very few scientific studies done on fenbendazole as a cancer treatment option, one such study suggests that fenbendazole has “been safely utilized as an anti-parasitic for various different animal species and could be repurposed for treating human malignancies.”
Another study states that the “repurposing of veterinary drugs showing promising results for human use can result in considerable time and cost reduction required to develop new drugs.”
Altogether, our findings show microtubule disruption, p53 stabilization and interference with glucose metabolism as collective underlying mechanisms of FZ induced preferential elimination of cancer cells both in vitro and in vivo.
Fenbendazole Side Effects in Humans
While little research has been done on the effects of fenbendazole and human consumption, studies have shown that the medication is typically tolerated well by humans, and thus far, has not reported any major side effects. While we can’t state that fenbendazole is safe for humans, the research appears promising.

According to a 2018 study, Fenbendazole (methyl N-(6-phenylsulfanyl-1H-benzimidazol-2-yl) carbamate) is a broad-spectrum benzimidazole anthelminthic approved for use in numerous animal species. Repurposing of veterinary drugs showing promising results for human use can result in considerable time and cost reduction required to develop new drugs. Fenbendazole is known to have a high safety margin and most species tolerate it very well. It has very low degree of toxicity and high degree of safety in experimental animals.
Another study also discussed the potential side effects of using fenbendazole in humans. “Based on limited human data it appears that doses up to 500 mg per person did not result in adverse effects,” the study states. “Moreover, single doses up to 2,000 mg per person were reported to cause no adverse effects.”
Fenbendazole Side Effects in Animals
Fenbendazole is safe to use in pets that are over six weeks in age. Although the medication is well tolerated by most animals, some potential mild side effects include:
- Loose stools or diarrhea
- Loss of appetite
- Salivation
- Vomiting
- Lethargy