Fenbendazole (veterinary anthelmintic)
Fenbendazole is a dog and livestock dewormer that is sold online as a cancer cure. It has never been approved for people, no trial has tested it in cancer, and doctors have reported severe liver injury in patients who took it.
Overview
Fenbendazole is an anthelmintic approved only for animals, and its human use has grown because social media promotes it as an anticancer drug (Thakurdesai case report 2024). The first case of biopsy-confirmed severe liver injury from self-administered fenbendazole was a 67-year-old woman whose jaundice cleared three months after she stopped (Thakurdesai case report 2024). A 65-year-old man with prostate cancer who alternated veterinary fenbendazole and ivermectin daily for three months developed hepatocellular liver injury with a bilirubin of 12.9 mg/dL, which normalised within six weeks of stopping (Powderly case report 2026). A three-patient case series claiming remissions was retracted by the journal in January 2026 (Retraction notice 2026). After a January 2025 podcast promoted fenbendazole with ivermectin for cancer, combined prescribing to US cancer patients rose 2.6-fold (Rockwell JAMA Network Open 2026). The FDA's guidance on products promoted as cancer cures without trial evidence applies here (FDA on products claiming to cure cancer).
- A 2016 personal story, shared worldwide
- Microtubule disruption in cell lines, as for many compounds that never become drugs
- Dish concentration versus human antiparasitic dosing
- Real repurposing runs through registered trials: aspirin, metformin, statins, mebendazole
Binds parasite tubulin and stops microtubule assembly, which is how it kills worms in dogs and livestock. Cancer cell lines respond to the same microtubule effect in a dish; that is laboratory evidence with no human trial behind it.
- A 2016 personal story, shared worldwide
- Microtubule disruption in cell lines, as for many compounds that never become drugs
- Dish concentration versus human antiparasitic dosing
- Real repurposing runs through registered trials: aspirin, metformin, statins, mebendazole
1.Fenbendazole (veterinary anthelmintic) binds its target with one end and an E3 ubiquitin ligase with the other.
Trials
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Veterinary paste is dosed for animals by weight, and 'one squirt' is not a human dose. Liver injury of this severity can be fatal and this patient was fortunate to present in time.
Measures the reach of the claim rather than the drug: tens of thousands of prescriptions written on the strength of a podcast, with no trial behind them.
Shows why single stories cannot settle the question: a melanoma this immunogenic can wax and wane on its own, and the improvement did not last.
This paper circulates widely online. Anyone quoting it should know that the journal has withdrawn it.
Fenbendazole has never been tested for safety in people. This is what that absence means in practice.
Latest papers
topQuery for this drug: (TITLE:"Fenbendazole" OR ABSTRACT:"Fenbendazole" OR TITLE:"veterinary anthelmintic" OR ABSTRACT:"veterinary anthelmintic" OR TITLE:"FBZ" OR ABSTRACT:"FBZ") AND (cancer OR tumor OR tumour OR oncology OR carcinoma OR lymphoma OR leukemia OR leukaemia OR myeloma OR sarcoma OR melanoma OR glioma). Results are unfiltered search hits about Fenbendazole (veterinary anthelmintic), not a curated reading list.
Similar pages
not linked directly; found by shared links- Key paperReal-world clinical outcomes of ivermectin and mebendazole in cancer patients: results from a prospective observational cohort (with 2026 expression of concern)
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- Key paperIvermectin in cancer treatment: should healthcare providers caution or explore its therapeutic potential?
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- TrialAtavistic chemotherapy: combinations of antibacterial, antifungal and antiprotozoal drugs in advanced cancer (Arguello clinic, status unknown)
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- Key paperCancer therapy using antiparasitic medications guided by acupuncture meridian assessment: a case series of six patients
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- Key paperLife-threatening neurotoxicity following off-label ivermectin use in metastatic breast cancer: a case report
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- Key paperThe multitargeted drug ivermectin: from an antiparasitic agent to a repositioned cancer drug
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- Key paperIvermectin treatment for gynecologic cancers: hope versus hype
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- Key paperIvermectin and gynecologic cancer: what's the data?
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