{"entity":{"id":"fenbendazole","kind":"drug","name":"Fenbendazole (veterinary anthelmintic)","aka":["FBZ"],"tldr":"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.","summary":"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 A three-patient case series claiming remissions was retracted by the journal in January 2026 (Retraction notice 2026).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).","status":"preclinical","asOf":"2026-09-24","wikipedia":"https://en.wikipedia.org/wiki/Fenbendazole","links":[{"label":"Thakurdesai case report 2024","url":"https://doi.org/10.14309/crj.0000000000001354"},{"label":"Powderly case report 2026","url":"https://doi.org/10.7759/cureus.108896"},{"label":"Retraction notice 2026","url":"https://doi.org/10.1159/000549387"},{"label":"Rockwell JAMA Network Open 2026","url":"https://doi.org/10.1001/jamanetworkopen.2026.16780"},{"label":"FDA on products claiming to cure cancer","url":"https://www.fda.gov/consumers/consumer-updates/products-claiming-cure-cancer-are-cruel-deception"}],"tags":[],"related":[],"cancers":[],"sections":[],"technologies":["fenbendazole-ivermectin-repurposing-claims"],"targets":[],"drugs":["ivermectin","mebendazole"],"companies":[],"institutions":[],"pathways":[],"terms":["hepatotoxicity","off-label","preclinical"],"trials":[],"people":[],"bottlenecks":["b-misinformation"],"keyPapers":["paper-thakurdesai-fenbendazole-liver-injury-2024","paper-powderly-fenbendazole-ivermectin-liver-injury-2026","paper-makis-fenbendazole-case-series-retracted-2025","paper-rockwell-ivermectin-benzimidazole-prescribing-jama-netw-open-2026"],"journals":[],"dependsOn":[],"notes":[],"provenance":{"editedBy":"OnCo agent (Claude Fable 5.1)","editedOn":"2026-09-24","note":"Written from cached ClinicalTrials.gov v2, Europe PMC, DailyMed, Drugs@FDA and WHO eEML responses; no figure appears without its source link."},"modality":"Veterinary benzimidazole anthelmintic; not approved for human use in any country","mechanism":"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.","approvals":[],"mechanismSteps":[],"toxicity":[],"access":[],"regulatoryEvents":[]},"route":"/drugs/fenbendazole/","neighbours":{"technology":[{"id":"fenbendazole-ivermectin-repurposing-claims","kind":"technology","name":"Fenbendazole, ivermectin and other internet 'repurposed cures'","route":"/technologies/fenbendazole-ivermectin-repurposing-claims/"}],"drug":[{"id":"ivermectin","kind":"drug","name":"Ivermectin","route":"/drugs/ivermectin/"},{"id":"mebendazole","kind":"drug","name":"Mebendazole","route":"/drugs/mebendazole/"}],"term":[{"id":"hepatotoxicity","kind":"term","name":"Hepatotoxicity (liver enzyme elevation)","route":"/terms/hepatotoxicity/"},{"id":"off-label","kind":"term","name":"Off-label","route":"/terms/off-label/"},{"id":"preclinical","kind":"term","name":"Preclinical","route":"/terms/preclinical/"}],"bottleneck":[{"id":"b-misinformation","kind":"bottleneck","name":"Misinformation and unproven therapies","route":"/bottlenecks/b-misinformation/"}],"paper":[{"id":"paper-powderly-fenbendazole-ivermectin-liver-injury-2026","kind":"paper","name":"Drug-induced liver injury following co-ingestion of veterinary fenbendazole and ivermectin for prostate cancer: a case report","route":"/key-papers/paper-powderly-fenbendazole-ivermectin-liver-injury-2026/"},{"id":"paper-rockwell-ivermectin-benzimidazole-prescribing-jama-netw-open-2026","kind":"paper","name":"Ivermectin-benzimidazole prescribing following celebrity endorsement","route":"/key-papers/paper-rockwell-ivermectin-benzimidazole-prescribing-jama-netw-open-2026/"},{"id":"paper-cheng-melanoma-ctdna-antiparasitic-front-oncol-2026","kind":"paper","name":"Metastatic melanoma with initial ctDNA decline and radiographic response during self-directed antiparasitic use: treatment effect or spontaneous regression?","route":"/key-papers/paper-cheng-melanoma-ctdna-antiparasitic-front-oncol-2026/"},{"id":"paper-makis-fenbendazole-case-series-retracted-2025","kind":"paper","name":"RETRACTED: Fenbendazole as an anticancer agent? A case series of self-administration in three patients","route":"/key-papers/paper-makis-fenbendazole-case-series-retracted-2025/"},{"id":"paper-thakurdesai-fenbendazole-liver-injury-2024","kind":"paper","name":"Severe drug-induced liver injury due to self-administration of the veterinary anthelmintic medication fenbendazole","route":"/key-papers/paper-thakurdesai-fenbendazole-liver-injury-2024/"}]}}