Fenbendazole
guinea pig
The Dose Guy’s verdictSep 1, 20264 sources
Skip it. Fenbendazole went viral as a cancer cure on the strength of anecdotes, not trials. There is not a single published human cancer trial behind the claim. The lab work is real, cancer cells die in dishes and mouse tumors shrink, though at least one mouse lymphoma model showed no benefit at all, and none of it has been tested in a person. The human data that does exist is a growing list of liver injury case reports.
What it is
Fenbendazole is a veterinary dewormer, a benzimidazole anthelmintic given to dogs and livestock to kill parasites. The anticancer story came from forums and social media claiming it cured human cancers off-label, and the proposed mechanism is real enough at the bench: fenbendazole binds tubulin, disrupts the cell skeleton, and interferes with glucose metabolism in cancer cells. The trouble is that killing cancer cells in vitro is easy. The question is always whether a drug does it inside a living person at a dose the liver tolerates, and nobody has tested that.
What the research shows
No human cancer trial exists. The lab evidence is consistent but stuck at the bench, and the one publication that tried to build a human story was retracted:
Realistic protocols
I am not building a dosing protocol for a veterinary dewormer with no human cancer evidence and a growing file of liver injuries. The dose that circulates online is typically 222 mg every other day or three days on, four days off, borrowed from the dog dose and scaled by body weight. That is lore, not evidence. If you run it anyway, get liver enzymes checked before you start and recheck them a few weeks in, because the injury pattern in the case reports is hepatocellular and showed up within weeks. Keep the course short. Do not drink on it, your liver is already doing something it was not designed for and alcohol is the last thing to pile on. Do not stack it with other drugs your liver is clearing, especially immunotherapy, where one case report scored RUCAM 8 for probable causality before immunotherapy was restarted without recurrence. And do not confuse a mouse xenograft with a reason to skip or delay real oncology care.
Side effects
The human safety data is almost entirely case reports of things going wrong:
