Ivermectin and Mebendazole, and What the Cancer Research Shows

Patients ask me about these two drugs almost every week, and the question is nearly always the same. Someone has read that a cheap antiparasitic cures cancer, or that ivermectin with mebendazole is what oncologists won't tell you about, and wants to know whether there's anything to it.

Two of the most-used drugs in medical history

Ivermectin came out of a single soil microbe collected in Japan in the 1970s, and its discovery earned Satoshi Ōmura and William Campbell a share of the 2015 Nobel Prize in Physiology or Medicine. Crump and Ōmura, in the Proceedings of the Japan Academy in 2011, described a drug that treats onchocerciasis (river blindness), strongyloidiasis, lymphatic filariasis and scabies, and anchors two global elimination campaigns in which well over 200 million people take it each year [1]. It opens glutamate-gated chloride channels, paralyzing nematodes and insects while leaving vertebrates largely alone, which is why a drug this lethal to worms is so gentle on people [1].

Mebendazole, a benzimidazole introduced for human use in 1971, treats the intestinal worms much of the world still carries, including hookworm, whipworm, roundworm and pinworm. Chai and colleagues, reviewing the benzimidazoles in the Korean Journal of Parasitology in 2021, explained that they block the parasite's microtubule system, the internal scaffolding a cell uses to divide and move its cargo, which starves the worm of glucose [2]. Both drugs are FDA-approved for parasitic infections, while a compounded capsule combining them isn't.

Why cancer researchers took an interest

Microtubules are the reason, because the protein mebendazole binds, tubulin, is also the target of two workhorse chemotherapy drugs, vincristine and paclitaxel, which attach at different sites on the same structure and kill dividing cells by wrecking the spindle that pulls chromosomes apart. A drug that hits tubulin, costs pennies, and carries a fifty-year safety record is worth a look.

Bai and colleagues at Johns Hopkins found this by accident while treating a pinworm outbreak in their animal facility, when the antiparasitic turned out to inhibit brain tumor growth. In Neuro-Oncology in 2011 they showed that mebendazole disrupted microtubule formation in glioblastoma cells and extended mean survival by up to 63 percent in two mouse models, at doses known to be safe in humans [3]. Ivermectin has its own preclinical file, and Melotti and colleagues reported in EMBO Molecular Medicine in 2014 that it blocks WNT-TCF signaling, a growth pathway that runs abnormally in colon and lung cancers, and slowed WNT-driven tumors in mice without obvious toxicity [4].

Mouse survival isn't human survival, and many compounds with better preclinical data than these two have failed once they reached human trials.

What has happened in actual patients

Far less has happened than the internet suggests. The best human study of either drug in cancer is a phase 1 trial, which by design tests safety and dose rather than whether a treatment works. Gallia and colleagues gave escalating doses of mebendazole with temozolomide to 24 patients with newly diagnosed high-grade glioma and reported the results in Neuro-Oncology Advances in 2021. Patients tolerated doses up to 200 mg/kg per day, four patients at the top dose developed grade 3 liver enzyme elevations that reversed on dose reduction, and median overall survival was 21 months [5]. With no control group, that trial established a tolerated dose and nothing more.

The one efficacy signal from a prospective trial went the wrong way. A phase 2a study in Scientific Reports in 2021 treated refractory gastrointestinal cancer with dose-adjusted mebendazole up to 4 g per day, and although no severe adverse effects occurred, all ten patients progressed, four of them meeting criteria for hyperprogression [6].

What remains are case reports, the best known of which comes from Dobrosotskaya and colleagues, who described a 48-year-old man with metastatic adrenocortical carcinoma that had progressed through mitotane, chemotherapy and radiation, whose metastases regressed and then held stable for 19 months on mebendazole alone before progressing at 24 months [7]. Two such reports exist for mebendazole in the published literature [2]. I take them seriously as leads, though a case report can't establish that a drug works, because the patients who don't respond are never written up.

In 2026 a telemedicine platform published the first study of the combination itself, a prospective observational cohort of 197 cancer patients prescribed compounded ivermectin and mebendazole capsules, of whom 122 completed six-month follow-up, with 48.4 percent reporting tumor regression or no evidence of disease [8]. The outcomes were self-reported rather than verified by imaging or pathology, there was no control group, and more than a quarter of the patients were on chemotherapy at the same time. Within days the journal issued a formal Expression of Concern over the verifiability and statistical reliability of the dataset and its ethical oversight, and it opened a data integrity audit [9]. No randomized controlled trial has shown that ivermectin, mebendazole, or the two together treat any cancer in humans.

The lesson the COVID years already taught

Caly and colleagues reported in Antiviral Research in April 2020 that ivermectin cut SARS-CoV-2 RNA roughly 5,000-fold in infected cells in a dish, and that single result launched a global movement [10]. Two months later, Schmith and colleagues showed in Clinical Pharmacology and Therapeutics that the concentration producing half of that inhibition was more than 35 times the peak blood level of the approved dose, and that even ten times that dose wouldn't reach it [11]. The randomized trials then delivered the verdict. TOGETHER, in the New England Journal of Medicine in 2022, gave symptomatic outpatients with risk factors ivermectin 400 mcg/kg for three days or placebo and found no reduction in hospitalization or prolonged emergency observation [12]. ACTIV-6, in JAMA the same year, randomized 1,591 outpatients and found a median recovery time of 12 days on ivermectin against 13 on placebo, with no difference in hospitalization or death [13].

Nobody should be embarrassed for having been curious about that first paper, and the people who ran the trials to settle it did the right thing. A drug concentration in a plastic dish tells you almost nothing about what happens in a person, which is why the cell-line cancer data isn't clinical evidence either.

Safety

At approved antiparasitic doses ivermectin is well tolerated. Guzzo and colleagues gave 68 healthy adults escalating doses up to 120 mg, ten times the highest FDA-approved dose, and found no central nervous system toxicity and adverse events no more frequent than with placebo [14]. Neurotoxicity does occur with overdose, mostly in people taking veterinary products or large repeated doses, and ivermectin interacts with warfarin while drugs that inhibit P-glycoprotein or CYP3A4 raise its levels.

Mebendazole is the one that needs monitoring. The cancer studies use high, prolonged doses rather than the two- or three-day courses used for worms, and at the top dose of the phase 1 trial a quarter of the patients developed liver enzyme elevation [5]. Prolonged benzimidazole therapy has also caused bone marrow suppression, including reversible marrow aplasia in a patient given large doses for a hydatid cyst [2,15]. Anyone taking it beyond a few days needs periodic blood counts and liver enzymes, and neither drug belongs in pregnancy.

Where I land, and what to do

If you have cancer, these drugs aren't a substitute for treatment with proven survival benefit. Don't delay or stop oncologic care for them, and don't take them quietly, since a rising ALT on mebendazole can look exactly like a chemotherapy complication and your oncologist needs to know. We aren't an oncology practice, and this post isn't a regimen.

My read is that mebendazole's microtubule mechanism is a legitimate research lead that deserves properly randomized trials, and that ivermectin's anticancer case rests almost entirely on cells and mice. The honest answer today is unproven, which is different from disproven and also different from promising.

What I'd do with this is narrower. Take these drugs for what they're approved to treat, and ask your physician for stool studies or serology before assuming a parasite explains your symptoms. If you want to try them against cancer, find a registered trial at clinicaltrials.gov rather than a protocol from the internet, and ask what the control arm gets. Put the rest of your effort where the evidence is strongest, since visceral fat behaves like an endocrine organ that drives tumor growth, and the populations that stay free of cancer tell you more about prevention than any repurposed pill does.

Ask a provider about ivermectin + mebendazole

References

1. Crump A, Ōmura S. Ivermectin, 'wonder drug' from Japan: the human use perspective. Proc Jpn Acad Ser B Phys Biol Sci. 2011. PMID: 21321478
2. Chai JY, Jung BK, Hong SJ. Albendazole and mebendazole as anti-parasitic and anti-cancer agents: an update. Korean J Parasitol. 2021. PMID: 34218593
3. Bai RY, Staedtke V, Aprhys CM, et al. Antiparasitic mebendazole shows survival benefit in 2 preclinical models of glioblastoma multiforme. Neuro Oncol. 2011. PMID: 21764822
4. Melotti A, Mas C, Kuciak M, et al. The river blindness drug ivermectin and related macrocyclic lactones inhibit WNT-TCF pathway responses in human cancer. EMBO Mol Med. 2014. PMID: 25143352
5. Gallia GL, Holdhoff M, Brem H, et al. Mebendazole and temozolomide in patients with newly diagnosed high-grade gliomas: results of a phase 1 clinical trial. Neurooncol Adv. 2021. PMID: 33506200
6. Mansoori S, Fryknäs M, Alvfors C, et al. A phase 2a clinical study on the safety and efficacy of individualized dosed mebendazole in patients with advanced gastrointestinal cancer. Sci Rep. 2021. PMID: 33903692
7. Dobrosotskaya IY, Hammer GD, Schteingart DE, et al. Mebendazole monotherapy and long-term disease control in metastatic adrenocortical carcinoma. Endocr Pract. 2011. PMID: 21454232
8. Hulscher N, Victory K, Thorp JA, et al. Real-world clinical outcomes of ivermectin and mebendazole in cancer patients: results from a prospective observational cohort. Anticancer Res. 2026. PMID: 42203321
9. Editorial Board. Expression of concern. Anticancer Res. 2026. PMID: 42300708
10. Caly L, Druce JD, Catton MG, et al. The FDA-approved drug ivermectin inhibits the replication of SARS-CoV-2 in vitro. Antiviral Res. 2020. PMID: 32251768
11. Schmith VD, Zhou JJ, Lohmer LRL. The approved dose of ivermectin alone is not the ideal dose for the treatment of COVID-19. Clin Pharmacol Ther. 2020. PMID: 32378737
12. Reis G, Silva EASM, Silva DCM, et al. Effect of early treatment with ivermectin among patients with Covid-19. N Engl J Med. 2022. PMID: 35353979
13. Naggie S, Boulware DR, Lindsell CJ, et al. Effect of ivermectin vs placebo on time to sustained recovery in outpatients with mild to moderate COVID-19: a randomized clinical trial. JAMA. 2022. PMID: 36269852
14. Guzzo CA, Furtek CI, Porras AG, et al. Safety, tolerability, and pharmacokinetics of escalating high doses of ivermectin in healthy adult subjects. J Clin Pharmacol. 2002. PMID: 12362927
15. Fernández-Bañares F, González-Huix F, Xiol X, et al. Marrow aplasia during high dose mebendazole treatment. Am J Trop Med Hyg. 1986. PMID: 3953948