Drug-Induced Liver Injury Following Co-ingestion of Veterinary Fenbendazole and Ivermectin for Prostate Cancer: A...

The self-administration of veterinary-grade anthelmintics, such as fenbendazole and ivermectin, has gained visibility in online communities due to unverified claims regarding potential anticancer effects. Despite these claims, these agents lack human regulatory approval due to unestablished safety profiles. We report a rare case of severe drug-induced liver injury (DILI) in a 65-year-old male with prostate cancer resulting from the concurrent ingestion of veterinary-grade fenbendazole and ivermectin. The patient presented to his primary care provider with a 2-week history of fatigue, jaundice, and abdominal pain following a 3-month regimen of alternating these agents daily at a dosage of "one squirt" (estimated to be 0.18 mg/kg of ivermectin and 0.98 mg/kg of fenbendazole) based on advice from online cancer support groups. Initial laboratory studies revealed profound transaminase elevations, with alanine aminotransferase (ALT) at 1764 U/L, aspartate aminotransferase (AST) at 1132 U/L, and a total bilirubin of 12.9 mg/dL. An R-value of 37.50 confirmed a hepatocellular injury pattern, while an extensive workup ruled out viral, autoimmune, and biliary etiologies. Following the complete cessation of both agents, transaminase levels decreased by 58% within 9 days and normalized within 6 weeks. A Roussel Uclaf Causality Assessment Method (RUCAM) score of 9 indicated a "highly probable" causal relationship between the anthelmintics and the acute liver injury. This case highlights the significant hepatotoxic risks associated with veterinary-grade therapies driven by medical misinformation. Overall, this case emphasizes the need for physicians to maintain a high index of suspicion for alternative therapies in oncology patients.