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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.
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 A three-patient case series claiming remissions was retracted by the journal in January 2026 (Retraction notice 2026).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).
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.
1.Fenbendazole (veterinary anthelmintic) binds its target with one end and an E3 ubiquitin ligase with the other.
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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 Anyone quoting it should know that the journal has withdrawn it.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.
Query 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.
Shares Off-label, Fenbendazole, ivermectin and other internet 'repurposed cures', Mebendazole, Ivermectin.
Shares Off-label, Fenbendazole, ivermectin and other internet 'repurposed cures', Preclinical, Ivermectin.
Shares Fenbendazole, ivermectin and other internet 'repurposed cures', Mebendazole, Ivermectin, Misinformation and unproven therapies.
Shares Fenbendazole, ivermectin and other internet 'repurposed cures', Mebendazole, Ivermectin, Misinformation and unproven therapies.
Shares Off-label, Ivermectin, Misinformation and unproven therapies.
Shares Fenbendazole, ivermectin and other internet 'repurposed cures', Preclinical, Ivermectin.
Shares Fenbendazole, ivermectin and other internet 'repurposed cures', Ivermectin, Misinformation and unproven therapies.
Shares Fenbendazole, ivermectin and other internet 'repurposed cures', Ivermectin.