Fenbendazole is a benzimidazole anthelmintic commonly used to treat parasitic infections in dogs, such as roundworms, hookworms, whipworms, and certain tapeworms. Its standard administration involves a dosage of 50 mg/kg (22.7 mg/lb) of body weight daily for three consecutive days. This regimen is generally well-tolerated, with minimal side effects.
Safety and Risks:
While short-term use of fenbendazole is considered safe, extended or off-label use has been associated with significant risks. The FDA has received reports of bone marrow hypoplasia or pancytopenia in dogs treated with fenbendazole beyond the recommended duration, with treatment lengths ranging from 5 to 14 days. These conditions involve a decrease in bone marrow activity, leading to reduced blood cell production.
Additionally, studies have indicated that fenbendazole may affect the bone marrow and immune system. Reports have documented myelosuppression (bone marrow suppression) in various species, including dogs, especially with high doses or prolonged administration.
Use in Cancer Treatment:
Interest in fenbendazole as a potential cancer treatment has emerged due to anecdotal reports and preliminary studies. Some in vitro (lab-based) studies have demonstrated that fenbendazole can inhibit tumor cell growth by disrupting microtubule formation, affecting glucose metabolism, and inducing cell cycle arrest in various cancer cell lines.
However, these findings are primarily from laboratory studies, and clinical evidence supporting fenbendazole’s efficacy in treating cancer in dogs is lacking. Researchers are still in the early stages of testing fenbendazole as a cancer treatment, and it has not been tested for efficacy in any specific cancer type yet.
Cancers Targeted and Not Targeted:
Due to the limited research, it is unclear which specific cancers fenbendazole may effectively target in dogs. The original tumor model affected was lymphoma, but more research is needed to determine its efficacy across various cancer types. Without comprehensive studies, it’s impossible to delineate which cancers fenbendazole may or may not target.
Conclusion:
While fenbendazole is a well-established dewormer for dogs (and even then we have safer options), its use as a cancer treatment remains experimental and is not supported by robust clinical evidence. Extended or off-label use carries significant risks, including severe bone marrow suppression. Dog owners should consult with their veterinarians before considering any off-label use of fenbendazole, especially for conditions like cancer, to thoroughly discuss potential benefits and risks.
FenBen is not recommended in my approach to supporting dogs.