Mebendazole
Also called: Vermox.
Last reviewed 2026-09-16. How this works.
When to call your team
Contact your care team the same day if you notice:
- yellowing of the eyes or skin
- urine that is much darker than usual
- pain or tenderness under the ribs on the right side
- feeling sick, with no appetite, for more than a day or two
- feeling unusually tired or generally unwell
A trial of mebendazole recorded liver enzyme changes in some people, which reversed when the amount was reduced. These are reasons to make a phone call. They are not a diagnosis, and this page cannot tell you what is causing them. Telling your team what you are taking is the only way anyone can check.2
These are reasons to make contact, not a diagnosis. Whatever you are taking or thinking of taking, the people treating you can only weigh it if they know about it.
This block is about what to watch for, and it is not all this page holds: what has been recorded about harm is below. Nothing in this block is an all-clear for a question it does not mention.
Treating cancer Grade C
Human evidence exists and does not settle it.
Harm has been recorded in people for this claim. The grade measures how strong the evidence for benefit is; it says nothing about the harm, and the two are read from different parts of this page.
One small trial found a benefit from this worming drug, but no trial has compared care with it against care without it.
One small positive randomised trial, and no trial with a mebendazole-free comparator.
The harm
In the phase 1 study, some people at the highest amount developed liver enzyme changes, which reversed when the amount was reduced. This is the reason the warning signs block on this page exists.2
The claim
Mebendazole is a worming drug used in people for decades. The claim is that it also acts against cancer, and of the antiparasitics it is the one with the most human evidence behind it.
What it does
Like other benzimidazoles it binds tubulin and disrupts the scaffolding a cell uses to divide. Unlike fenbendazole it is licensed for human use, so it has been given to people under supervision and studied.
The evidence
A randomised, double-blind, placebo-controlled trial in metastatic bowel cancer added mebendazole to standard chemotherapy. The response rate was 65 percent in the mebendazole arm against 10 percent in the placebo arm, and progression-free survival was longer.1
That result is striking, and the book's reading is that a 10 percent response rate is lower than the control regimen would normally produce, which makes the comparison hard to interpret. That reading is the book's own and is not a finding of the paper.
A phase 1 study in newly diagnosed high-grade glioma established that mebendazole could be given alongside standard treatment. Its authors state plainly that the study had too few patients to demonstrate efficacy and that randomised trials should follow.2
A randomised open-label phase II trial in recurrent glioblastoma compared mebendazole with one chemotherapy against mebendazole with another. Both arms received mebendazole, so the trial cannot show whether mebendazole contributed anything at all.3
The studies this rests on
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Mebendazole added to chemotherapy in metastatic colorectal cancer1
A randomised trial, double blind, phase 2, measured a clinical outcome, 40 participants.
higher overall response rate and longer progression-free survival in the mebendazole arm.
overall response rate: 65 percent against 10 percent; the paper reports P as 0.000
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Mebendazole and temozolomide in newly diagnosed high-grade glioma2
A trial with no comparison group, open label, phase 1, measured safety, 24 participants.
dose-escalation and safety study; the authors state it had too few patients to demonstrate efficacy.
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Mebendazole plus lomustine or temozolomide in recurrent glioblastoma3
A randomised trial, the comparator group also received something, open label, phase 2, measured survival.
nine-month overall survival of 36 percent and 45 percent in the two arms, both of which received mebendazole.
What is absent
No trial has compared standard treatment with mebendazole against standard treatment without it in a brain tumour. The randomised trial in recurrent glioblastoma gave mebendazole to both arms.
Scope: brain tumours.
Established by trial scope, checked 2026-09-16. Result: both arms of the only randomised brain tumour trial in this record received mebendazole.32
The single positive randomised trial has not been repeated by an independent group.
Scope: bowel cancer.
Nobody has run a search to establish this, so it is the register’s reading of what exists rather than a gap somebody has looked for and confirmed.
What to ask
Is there any trial evidence for mebendazole that compares treatment with it against treatment without it?
The dish-to-person gap
The register records no human pharmacokinetic measurement for mebendazole. The phase 1 study cited here reports that plasma levels were adequate to proceed, but the chapter note carries no concentration figure, so none is recorded.
Interactions
No interaction between mebendazole and a cancer treatment class has been studied in people. An empty list here means nobody has looked, not that nothing would happen.
Nobody having looked is not the same as nothing being there. That is what this line says and all it says.
The whole interaction list, and how to turn it into a pharmacy review request.
Find a trial instead
A recruiting trial is the same decision with monitoring and liver testing attached.
Search ClinicalTrials.gov for recruiting studies of mebendazole
A trial is the same decision with monitoring, a known preparation and a doctor who knows what else you are taking.
References
Mebendazole: from an anti-parasitic drug to a promising candidate for drug repurposing in colorectal cancer. Life Sciences, 2022.
How this was reached: transcribed from chapter note, via docs/CHAPTER-NOTES.json, chapter 13 note 1.
Gallia GL, Holdhoff M, Brem H, Joshi AD, Blakeley J, Sengupta S, Jarrell TC, Wollett J, Szajna K, Helie N, Mattox AK, Ye X, Rudek MA, Riggins GJ. Mebendazole and temozolomide in patients with newly diagnosed high-grade gliomas: results of a phase 1 clinical trial. Neuro-Oncology Advances 2021;3(1):vdaa154.
doi:10.1093/noajnl/vdaa154 · PubMed 33506200 · PMC7817892
How this was reached: transcribed from chapter note, via docs/CHAPTER-NOTES.json, chapter 13 note 2. The author string is abbreviated in the source that was read and has not been expanded.
Mebendazole plus lomustine or temozolomide in patients with recurrent glioblastoma: a randomised open-label phase II trial.
How this was reached: transcribed from chapter note, via docs/CHAPTER-NOTES.json, chapter 13 note 3.