Ivermectin, Fenbendazole and Mebendazole in Cancer: The Evidence and the Protocols

Key Takeaways:

• Mebendazole is the only one of the three with completed cancer trials; its strongest result is a 40-patient randomized trial in metastatic colorectal cancer in which adding it to chemotherapy raised the response rate from 10% to 65%, while mebendazole taken alone failed in refractory gastrointestinal cancer.
• No trial of ivermectin as a cancer treatment has been completed, and fenbendazole, a veterinary dewormer, has never been tested in any human dosing, safety or efficacy trial.
• The main measured harm of unproven cancer treatment is what people give up for it: in a national registry of 1.9 million patients with curable cancers, those also using unproven therapies refused standard treatment far more often and had about twice the risk of death.

Ivermectin, mebendazole and fenbendazole are old, inexpensive antiparasitic drugs that kill cancer cells in the laboratory, and a growing number of people with cancer now take them. This guide looks at antiparasitic drugs for cancer from both sides at full strength: the laboratory case, every completed and ongoing human trial we could verify, the popular protocols, including those promoted by Joe Tippens and William Makis, the doses actually used and where each one comes from, and the safety record. Major cancer guidelines do not endorse these drugs. That reflects missing trials more than disproven drugs, so rather than dismiss them, we grade the evidence that does exist. Every anticancer use described here earns a C (early evidence) or a D (tested, did not help); none reaches an A or a B.

Quick reference: what to do if you are considering these drugs

Five actions matter more than anything else on this page:

• Keep the treatment that works. Where surgery, radiation, hormone therapy, chemotherapy or immunotherapy can cure or control your cancer, anything you add goes alongside it, never in place of it.
• Tell your oncologist. These drugs change liver tests and blood counts, and liver injury from them can look like an immunotherapy side effect.
• Know which drug has which evidence. Mebendazole has completed human trials; ivermectin has two cancer trials registered, one recruiting; fenbendazole has never been tested in a human trial.
• Use human pharmaceutical products. Veterinary pastes and granules are made and dosed for animals, and they figure in the published liver-injury reports.
• Monitor. Liver tests and a blood count before you start, at 2 and 4 weeks, then monthly.

Know the numbers:

• Mebendazole: approved worm doses run from 100 mg to a single 500 mg; cancer trials used 500 mg twice daily up to 1,600 mg three times daily (one glioma trial went higher by weight), taken with a fatty meal.
• Ivermectin: the approved dose is 150–200 µg/kg once; a university trial that is not yet recruiting plans to test 200 or 400 µg/kg on three days each week; popular protocols use 0.5–2 mg/kg, with no long-term safety study at those doses.
• Fenbendazole: 222 mg a day (the Tippens protocol) to 1,000 mg three times a week; no human dosing study exists.

Stop and call your clinician the same day for:

• Liver warning signs: yellow eyes or skin, dark urine, pale stools, itching, or right-sided belly pain.
• Blood count warning signs: sore throat or mouth sores, which can signal a low white count. A fever of 100.5 °F (38 °C) or more during chemotherapy means calling your oncology team now, not later that day.
• Nerve symptoms (ivermectin): blurred vision, tremor, or mild unsteadiness. New confusion, trouble staying awake, seizures or trouble breathing call for 911.
• Skin: a blistering or peeling rash, especially on mebendazole with metronidazole, needs emergency care.

What are these drugs, and how might they work against cancer?

Three antiparasitic drugs sit at the center of this story. Mebendazole is a human deworming drug introduced in 1971 [1]. Ivermectin, FDA-approved for human use in 1987, has been taken by millions of people for parasitic infections [2]. Fenbendazole is a close chemical cousin of mebendazole approved only for animals; it is sold over the counter as a dewormer for cats and dogs [3]. Albendazole, another cousin, occasionally appears in the same protocols.

The cancer interest began by accident. At Johns Hopkins, researchers noticed that mice given fenbendazole for pinworms stopped growing implanted brain tumors. Screening related drugs pointed to mebendazole, which killed glioblastoma cells at 0.1–0.3 micromolar and extended survival by up to 63% in mouse glioma models [4]. Separately, in another Johns Hopkins laboratory, a human lymphoma model failed to grow in mice fed fenbendazole plus extra vitamins; in a follow-up study the combination significantly inhibited tumor growth, while neither fenbendazole nor the vitamins alone altered it [5].

The proposed mechanisms, all of them laboratory findings:

• Microtubules. Mebendazole and fenbendazole bind tubulin, the scaffolding a cell needs to divide, a target they share with some chemotherapy drugs; fenbendazole binds it only moderately [4, 6].
• Glucose and p53. Fenbendazole reduced glucose uptake, GLUT transporters and the glycolytic enzyme hexokinase II, and moved the tumor-suppressor protein p53 into mitochondria, in cell culture and in tumors grown in mice [6].
• Blood vessels, Hedgehog signaling and DNA repair. In models, mebendazole blocks new blood-vessel growth, interferes with Hedgehog signaling (relevant to medulloblastoma), inhibits kinases and impairs DNA repair [7].
• Ivermectin’s targets. PAK1 and Akt/mTOR, WNT-TCF signaling, the P-glycoprotein drug pump, chloride channels, and stem-like cancer cells [2, 8].
• Immune effects. In mouse breast cancer, ivermectin turned “cold” tumors “hot” and worked with anti-PD-1 immunotherapy, though neither drug worked alone [9]. In 2026 the journal attached an expression of concern to that paper over duplicated images in one figure, and the original data were no longer available.

The concentration problem is the central open question. A standard 12 mg ivermectin dose peaks at about 30–47 ng/mL in the blood, roughly 0.03–0.05 micromolar [10]. Most laboratory work uses far more; the group that set out to test “clinically feasible” levels used 5 micromolar, about a hundredfold higher, and found breast and ovarian lines the most sensitive [11]. Mebendazole has the opposite problem: it is potent in the dish but poorly absorbed, and in one trial only 5 of 10 patients reached the target blood level despite doses up to 4 g a day [12]. Whether these mechanisms operate at doses people can actually take is exactly why cell and mouse results so often fail to carry over.

The case for trying them, and the case for skepticism

The case for trying them. Two of the three are approved human drugs with decades of use, they are inexpensive, and they act on several cancer pathways at once. They have been tolerated at doses far above antiparasitic use: mebendazole up to 200 mg/kg a day in adults with glioma, and ivermectin at up to ten times the highest approved dose in healthy volunteers [1, 13]. One randomized trial in metastatic colorectal cancer reported a response rate of 65% with mebendazole added to chemotherapy versus 10% without [14]. In newly diagnosed high-grade glioma, mebendazole added to temozolomide was followed by a median survival of 21 months, with 25% of patients alive at four years, in an uncontrolled phase 1 trial [1]. Case reports describe durable control, such as 19 months of stable metastatic adrenal cancer on mebendazole alone after standard drugs failed [15]. And patent-expired drugs rarely attract the industry money that funds large trials; one group argued that randomized trials of such drugs may be neither economically viable nor, in some settings, ethically simple [16]. The absence of a large trial reflects funding at least in part, and it is not proof that the drugs fail.

The case for skepticism. No randomized trial of ivermectin or fenbendazole in cancer has been completed. Other mebendazole trials were disappointing: taken alone in refractory gastrointestinal cancer, every patient progressed and the trial stopped [12], and added to chemotherapy in recurrent glioblastoma it missed its pre-set survival target in both arms [17]. A 2026 systematic review concluded that clinical evidence does not yet show meaningful efficacy in brain tumors [7]. The best-known success stories involved people who were also receiving effective standard treatment, a three-patient case series was retracted, and the largest cohort carries an expression of concern. Veterinary fenbendazole has produced documented liver injury [3].

Both cases are partly right. The honest summary: plausible, cheap and mostly tolerable, but unproven in humans, with the best human signal belonging to mebendazole.

Mebendazole: the drug with human trials

Mebendazole is the only one of the three with completed cancer trials, from Johns Hopkins, Tata Memorial in India, Uppsala in Sweden and a group in Egypt.

• Newly diagnosed high-grade glioma (phase 1, 24 adults). Mebendazole was added to temozolomide after radiation at 25 to 200 mg/kg a day. Median survival was 21 months, with 41.7% of patients alive at two years and 25% at three and four years; four patients at the top dose developed grade 3 liver-enzyme rises after a month that reversed on lowering or stopping the dose [1]. Without a control group, these figures cannot be credited to mebendazole.
• Recurrent glioblastoma (randomized phase II, 88 adults), grade C. Mebendazole 1,600 mg three times daily with temozolomide, or 800 mg three times daily with lomustine. Nine-month survival was 36.6% and 45% respectively, short of the 55% bar; 28.6% of patients were quite ill at entry, which the authors think dragged results down, and with mebendazole in both arms the trial could not measure what it added [17].
• Metastatic colorectal cancer (randomized, double-blind, 40 adults), grade C. Mebendazole 500 mg twice daily for 12 weeks alongside FOLFOX4 plus bevacizumab: response rate 65% versus 10%, median progression-free survival 9.25 versus 3 months [14]. It is a small trial registered after the fact, and effects this large need replication.
• Refractory gastrointestinal cancer, mebendazole alone (phase 2a, 10 treated), grade D. Doses up to 4 g a day aimed at a blood level of 300 ng/mL; all patients progressed by 8 weeks, and four met criteria for accelerated growth [12].
• Children and young adults. Two phase 1 trials in brain tumors found high doses tolerable; responses appeared when mebendazole was combined with bevacizumab and irinotecan, but single-agent activity was limited [18, 19].

Form matters. Mebendazole exists in three crystal forms, called polymorphs. In mice, polymorph C reached effective brain levels with fewer side effects, polymorph B was more toxic, and polymorph A did nothing [20]. A 2026 review found that results in brain tumors depended on formulation [7]. It is worth asking the pharmacy which form it dispenses.

Ivermectin: laboratory promise, first trials under way

Ivermectin slows or kills cancer cells in dozens of laboratory models. In leukemia models, it killed leukemia cells at low micromolar levels in preference to normal blood cells, delayed tumor growth in three mouse models, and worked with the chemotherapy drugs cytarabine and daunorubicin [8]. Breast and ovarian lines were the most sensitive at 5 micromolar, and ivermectin worked with docetaxel, cyclophosphamide and tamoxifen in the dish [11].

No completed trial has tested ivermectin as a cancer treatment. The two registered trials both pair it with checkpoint immunotherapy, following the mouse work above. In healthy volunteers, single doses up to 120 mg, and 60 mg three times a week, were generally well tolerated with no sign of brain toxicity, and food raised exposure to a 30 mg dose 2.6-fold [13]. Those were short courses; the high daily doses in popular protocols, taken for months, have no comparable safety study. Anticancer use is graded C.

Interest is public and growing. After a January 2025 celebrity podcast endorsement, combined ivermectin-plus-benzimidazole prescribing across 67 US health systems roughly doubled (rate ratio 1.97) and tripled in the South, and the National Cancer Institute announced plans to study ivermectin [21].

Fenbendazole: a veterinary drug with no human trials

Fenbendazole has never been studied in a human dosing, safety or efficacy trial, and no trial is registered. What exists is laboratory work, animal studies and self-reported cases.

• Laboratory and animal data are mixed. It destabilized microtubules, cut glucose uptake and blocked human tumor xenografts in mice fed the drug [6]. But in mouse mammary tumors, the most intensive regimens did not slow growth or add to radiation [22]. And in the original lymphoma observation, fenbendazole alone did nothing; only the combination with vitamins did [5].
• Human reports. Anecdotes, the Tippens story and a retracted case series are covered under the protocols below. Almost none of them separates fenbendazole from the other treatments people were receiving. The exception is a 2020 report of an 83-year-old man with stage IV diffuse large B-cell lymphoma who declined chemotherapy, took fenbendazole with no other cancer treatment reported, and improved on PET scans over about nine months; peripheral neuropathy made him cut the dose, and his physicians wrote that whether the improvement was related to fenbendazole or other factors remains unknown [40]. One uncontrolled case cannot show cause.
• What is unknown. How much a person absorbs, what blood level a given dose produces, and what long-term use does. The known human harm is liver injury.

Anticancer use is graded C, with the thinnest evidence of the three.

Which trials are completed, and which are still running?

Every ClinicalTrials.gov entry below was checked on September 30, 2026; the Indian trial is taken from its published report. Status is the registry’s own, and a stale entry is labeled as such.

• NCT01729260 (Johns Hopkins): mebendazole plus temozolomide, newly diagnosed high-grade glioma, phase 1, 24 adults. Completed 2021; tolerable to 200 mg/kg/day; median survival 21 months, uncontrolled.
• CTRI/2018/01/011542 (India): mebendazole plus lomustine or temozolomide, recurrent glioblastoma, randomized phase II, 88 adults. Completed; missed its 9-month survival target in both arms.
• NCT03925662 (Egypt): mebendazole plus FOLFOX and bevacizumab, colorectal cancer. A 40-patient randomized trial citing this number was published in 2022 (response 65% vs 10%); the registry still reads “recruiting,” unchanged since April 2019.
• NCT03628079 (Sweden): mebendazole alone, refractory gastrointestinal cancer, phase 1/2. Terminated 2019 for “lack of effect”; all treated patients progressed.
• NCT02644291 (Johns Hopkins): mebendazole alone, recurrent pediatric brain tumors, phase 1. Completed 2022; tolerable, with limited single-agent activity.
• NCT01837862 (Northwell): mebendazole plus bevacizumab and irinotecan, pediatric glioma, phase 1/2. Active, not recruiting; completion estimated December 2027. In phase 1, 3 of 9 responded.
• NCT05318469 (Cedars-Sinai): ivermectin plus balstilimab or pembrolizumab, metastatic triple-negative breast cancer, phase 1/2, 34 planned. Recruiting; primary completion estimated October 2026. Early results presented as a 2025 conference abstract (ivermectin 30–60 mg on 3 days a week with balstilimab): of 8 evaluable, heavily pretreated patients, 1 had a partial response, 1 stable disease and 6 progressed; well tolerated; no comparison group.
• NCT07487805 (ICONIC, a university-led trial): ivermectin 200 or 400 µg/kg on days 1–3 weekly for 4 weeks in adults already on checkpoint immunotherapy, phase 2, 80 planned. Not yet recruiting; the primary endpoint is an immune-cell marker, not tumor response.
• NCT04443049 (India): mebendazole 100 mg twice daily plus lenvatinib, advanced liver cancer with cirrhosis, randomized, 170 planned. Status unknown; last updated 2021; no results.
• NCT02201381 (Care Oncology, METRICS): metformin, atorvastatin, doxycycline and mebendazole in any cancer. Withdrawn 2022; “prospective recruitment not possible.”
• NCT02366884 (private clinic): “atavistic chemotherapy” combining antiparasitic, antifungal and antibacterial drugs, phase 2. Status unknown since 2022; no results.
• Fenbendazole: no trial registered for any cancer.

Which cancers look most promising?

Ranked by the strength of the human evidence:

• High-grade glioma and glioblastoma (mebendazole). The most human data: phase 1 survival figures the authors called encouraging but not statistically significant, a retrospective clinic series (below), and a randomized phase II that did not meet its bar [1, 17]. The biology fits, because mebendazole reaches the brain [20, 7].
• Metastatic colorectal cancer (mebendazole with chemotherapy). The single most positive human result, from one small trial [14]. It is not a reason to take mebendazole alone: in refractory gastrointestinal cancer, mebendazole by itself failed [12].
• Triple-negative breast cancer and other immunotherapy-treated tumors (ivermectin). Mouse data, one trial recruiting and one not yet open; early conference results in 8 patients, with 1 partial response, have no comparison group [9].
• Leukemia, breast and ovarian lines (ivermectin) and medulloblastoma (mebendazole). Laboratory and animal evidence only [8, 11, 7].
• Everything else, including prostate, melanoma, pancreatic, lung and liver cancer, rests on individual reports (the prostate and melanoma cases in the retracted series among them) or on trials whose status is unknown.

What about the Tippens and Makis protocols?

Joe Tippens. In 2016 Joe Tippens, a businessman, was diagnosed with small-cell lung cancer and told he might have three months to a year. While enrolled in a clinical trial, he added fenbendazole with vitamin E, CBD oil and curcumin on a veterinarian’s suggestion; a PET scan three months later showed no cancer [23]. The trial he was in tested the immunotherapy drug pembrolizumab (Keytruda) at MD Anderson, which is the likelier explanation for his response. His story spread widely enough that fenbendazole sold out in South Korean pharmacies [24]. His current protocol (updated December 2025) is fenbendazole 222 mg (1 g of Panacur or Safe-Guard granules) every day plus four proprietary “Onco Adjunct” products [25]. Grade C: one confounded case, no controlled data.

William Makis. William Makis, a nuclear-medicine physician by training, advocates combining ivermectin with mebendazole or fenbendazole. The protocol he promotes was published in 2024 in the Journal of Orthomolecular Medicine, co-authored with 14 others including Paul Marik [26]. It grades cancers as low, intermediate or high grade and escalates by grade:

• Ivermectin: 0.5 mg/kg three times a week (low grade), 1 mg/kg three times a week (intermediate), 1–2 mg/kg a day (high grade).
• Mebendazole: 200, 400 or 1,500 mg a day by grade; fenbendazole 1,000 mg three times a week for high-grade cancers.
• Adjuncts: DON (a glutamine-blocking compound), intravenous vitamin C 1.5 g/kg two to three times a week, vitamin D up to 50,000 IU a day to a blood level of 80 ng/mL, zinc 1 mg/kg a day, a 900–1,500 kcal ketogenic diet, 3- to 7-day water fasts every 3–4 weeks, exercise three times a week, and hyperbaric oxygen.

Two of those components carry known risks. Zinc at 1 mg/kg is about 70 mg a day for a 70-kg adult, above the 40 mg adult upper limit, which was set because high intake causes copper deficiency. And DON is an experimental anticancer drug whose 1980 phase 1 trial found nausea with vomiting dose-limiting, frequent low platelets, mouth sores in 39% of patients and no definite responses [36].

The paper rests mainly on laboratory and animal studies and individual case reports; it presents no controlled or systematic outcome data. It does not specify taking the benzimidazoles with food or monitoring liver tests and blood counts during them, nor screening for G6PD deficiency, kidney disease and kidney stones before high-dose intravenous vitamin C, which the National Cancer Institute lists as risk factors for toxicity. Makis’s published outcome report, a three-patient fenbendazole case series, was retracted in January 2026 because the first author had offered services related to the topic without declaring it [27]. Read on its own terms, each patient was also on effective standard therapy: fulvestrant plus spinal radiation for breast cancer, androgen deprivation for prostate cancer, and two doses of nivolumab for melanoma, although the summary table lists only “fenbendazole, surgery, supplements” for that case [27]. Posts quoted in court filings claim roughly 7,500 cancer patients; we found no published outcome data for them. He has not held an active Alberta medical license since 2019, and in March 2026 an Alberta court permanently barred him from practicing medicine or offering health services there, stating that the case concerned unlicensed practice, not the efficacy of ivermectin [28]. Grade for the protocol as a whole: C.

Other published and clinic protocols.

• Care Oncology (metformin, atorvastatin, doxycycline, mebendazole) added to standard care. In a retrospective review of 95 patients with glioblastoma at a private, patient-funded clinic, median survival was 26.3 months, against 14.8–15.8 months in historical comparison groups [16]. Historical comparisons flatter self-selected, fitter patients, the journal posted an expression of concern in 2023, and the prospective study was withdrawn.
• The 2026 telemedicine cohort. 197 people with mixed cancers were prescribed compounded ivermectin 25 mg and mebendazole 250 mg; 122 answered a six-month survey, and 84.4% of them reported benefit. Outcomes were self-reported, there was no control group, and many were also receiving chemotherapy (28%), radiation (21%) or surgery (20%). The journal issued an expression of concern and opened an audit of ethics approval and source records; a September 2026 update records a change in the scope of that review and states that the audit described in the original notice is concluded, and the notice remains part of the publication record [29].

Doses, monitoring and how to do it safely

Each dose below is labeled by its source: a trial, a published protocol or a personal account. None is a proven cancer dose.

Alongside, never instead. The main measured harm of unproven cancer treatment is what people give up for it. Among 1.9 million US patients with curable cancers in a national registry, the 258 recorded as also using unproven therapies refused surgery, chemotherapy, radiation and hormone therapy far more often and had about twice the risk of death; once refusal was accounted for, the extra risk was no longer statistically significant [30]. Where standard treatment can cure or control your cancer, these drugs are an add-on at most. Replacing effective treatment with them is graded D.

Mebendazole (human drug, used off-label; grade C).

• What it is: an FDA-approved dewormer (Emverm, Vermox); approved worm doses run from 100 mg to a single 500 mg.
• How it works: binds tubulin; blocks VEGFR2 and Hedgehog signaling in models; polymorph C reaches the brain best.
• Doses used: in trials, 500 mg twice daily with colorectal chemotherapy, 800–1,600 mg three times daily with glioma chemotherapy, and up to 200 mg/kg/day in a phase 1. In the Makis protocol, 200–1,500 mg a day. Taken with a fatty meal.
• Side effects: liver-enzyme rises (grade 3 in 4 of 15 patients at the top trial dose) and low white counts at high or prolonged doses. Avoid combining it with metronidazole.

Ivermectin (human drug, used off-label; grade C).

• What it is: an FDA-approved antiparasitic (Stromectol and generics); the approved dose is 150–200 µg/kg once.
• How it works: in models, PAK1/Akt-mTOR and WNT blockade, chloride-channel stress, and immune activation with anti-PD-1 therapy.
• Doses used: the planned university trial tests 200 or 400 µg/kg on days 1–3 each week; the 2026 cohort used 25 mg capsules; the Makis protocol runs from 0.5 mg/kg three times weekly to 2 mg/kg daily. The label says to take it on an empty stomach with water; food raises blood levels about 2.5-fold, so take it the same way every time.
• Side effects: confusion, unsteadiness, visual change and seizures at high doses; it can raise the INR in people on warfarin; not for use in pregnancy.

Fenbendazole (veterinary only; grade C).

• What it is: an animal dewormer (Panacur, Safe-Guard) with no human formulation or approved human dose.
• How it works: a weak tubulin binder that lowers glucose uptake and hexokinase II and activates p53 in cell studies.
• Doses used: no trial dose exists. Tippens takes 222 mg daily; the retracted case series used 222–444 mg daily; the Makis protocol uses 1,000 mg three times weekly.
• Side effects: mild liver-enzyme rises are common, and severe liver injury with jaundice is documented in case reports, including in people on immunotherapy. It is inexpensive, which is part of its appeal, but product purity and dose accuracy are not regulated for humans.

Doing it well.

• One drug, human grade, a defined trial period. Mebendazole is the rational first choice because it has human-trial doses and safety data. Adding ivermectin makes it harder to tell which drug caused a benefit or a side effect. Avoid veterinary products: they are made and labeled for animals, and they figure in the published liver-injury reports [3, 31].
• Food. A fatty meal raises mebendazole absorption; for ivermectin, the label says to take it on an empty stomach with water, and food changes blood levels about 2.5-fold, so be consistent [32, 10].
• Monitoring. Before starting: liver tests (ALT, AST, bilirubin, alkaline phosphatase), a complete blood count, and an INR if you take warfarin. Repeat at 2 and 4 weeks, then monthly. That is a cautious schedule, because the glioma trial’s liver rises appeared around one month and its authors advise monthly blood counts and chemistry [1].
• Judge it by the scans and markers your oncologist already uses, on the usual schedule. Feeling better, or a single tumor-marker drop, is not a response; in the melanoma case above, a circulating tumor DNA marker fell to zero while the patient was also receiving nivolumab [27].
• With standard treatment. Mebendazole has been combined in trials with temozolomide, lomustine, FOLFOX with bevacizumab, and bevacizumab with irinotecan; the main toxicities reported were liver-enzyme rises and low blood counts [1, 17, 14, 18]. Ivermectin with checkpoint immunotherapy is being tested now; outside a trial, your oncologist should know before you start.
• Finding a supervising clinician. Ask your oncologist first; many will monitor labs even if they would not prescribe. An internal or integrative medicine physician can prescribe human-grade mebendazole or ivermectin off-label and coordinate care. The two registered ivermectin trials above are the most rigorous way to take it.

Side effects, liver injury and interactions

At approved doses, mebendazole and ivermectin have long safety records. At cancer-protocol doses the picture is thinner, and fenbendazole’s human safety is known only from case reports.

• Liver. Fenbendazole commonly causes mild enzyme rises and can cause clinically apparent liver injury [3]. Published cases include a man with prostate cancer who alternated veterinary fenbendazole and ivermectin daily for three months and presented with an ALT of 1,764 and a bilirubin of 12.9; he recovered within six weeks of stopping [31]. In a woman on nivolumab and relatlimab, fenbendazole liver injury mimicked immunotherapy hepatitis, a mix-up that can lead to unneeded steroids or stopped immunotherapy; she restarted immunotherapy safely after stopping fenbendazole [33]. Mebendazole at 200 mg/kg a day caused reversible grade 3 rises in 4 of 15 patients [1].
• Blood counts. Mebendazole at high or prolonged doses can cause neutropenia and agranulocytosis, and its label says to monitor blood counts [32]. Combined with bevacizumab and irinotecan in young patients, grade 3–4 neutropenia occurred in 3 of 10 [18].
• Nervous system (ivermectin). Drowsiness, confusion, coma and death have been reported at recommended doses as well as in overdose, which can also cause unsteadiness, tremor and seizures [10]. A 73-year-old woman with breast cancer who took high doses based on online advice had seizures and needed a ventilator, then recovered fully within 48 hours [34].
• Interactions. Ivermectin is broken down by CYP3A4 and interacts with the P-glycoprotein pump, so strong CYP3A4 blockers or inducers may change its levels; an increased INR has rarely been reported on warfarin [10, 2]. Mebendazole with metronidazole has caused Stevens-Johnson syndrome and toxic epidermal necrolysis [32]. Mebendazole can add to chemotherapy’s effect on blood counts.
• Who should not take them without specialist input: pregnancy (ivermectin’s label says not to use it, and mebendazole was embryotoxic in animals), existing liver disease or abnormal liver tests, low blood counts, warfarin, and anyone who has lived where the Loa loa eye worm is common (parts of central and west Africa), in whom ivermectin can trigger encephalopathy [10, 32].

Tell your team. In a South Korean survey of 86 people taking non-prescription dewormers for cancer, about half took them during chemotherapy, and 96.5% of those did not tell their clinicians [35].

Lifestyle and integrative foundations with stronger evidence

Several steps have stronger evidence and fewer unknowns, and they combine with any of the above.

• Exercise and nutrition during and after treatment have the most consistent evidence among self-directed measures. In the CHALLENGE trial, 889 people who had finished chemotherapy for colon cancer were randomized to three years of structured exercise or to health-education materials; exercise cut recurrence, new cancer or death by 28% (5-year disease-free survival 80% vs 74%), with more muscle and joint injuries [37].
• Fasting, carefully. Aggressive calorie restriction and multi-day water fasts, as in the Makis protocol, can worsen the weight and muscle loss many people with cancer already face; plan them with your oncology team if at all. A tested alternative is short: in the DIRECT trial of 131 women with breast cancer, a 3-day fasting-mimicking diet around each chemotherapy cycle was linked to more tumor responses [38].
• Vitamin D. A reasonable target is 40–60 ng/mL, reached with a measured level and no more than 2,000 IU a day unmonitored, which is lower than the Makis protocol’s 80 ng/mL target and 50,000 IU daily dose.
• Other repurposed and integrative options with their own evidence tiers: low-dose naltrexone, medicinal mushrooms (turkey tail’s PSK has the strongest oncology data), and high-dose intravenous vitamin C, which in a small randomized trial in metastatic pancreatic cancer was followed by a median survival of 16 versus 8.3 months when added to chemotherapy [39]. Protocol adjuncts such as CBD carry interactions of their own, so buy independently tested products.
• A survivorship plan that puts every drug and supplement on one list your team can see and, when cure is not the goal, palliative care early, which improves quality of life regardless of what else you choose.

Claim versus evidence: what is the bottom line?

• “These drugs kill cancer cells.” Supported, in the laboratory, often at concentrations above what standard doses reach in the blood.
• “Mebendazole improves outcomes with chemotherapy.” Partly supported: one small positive trial in colorectal cancer; a larger glioblastoma trial missed its target.
• “Mebendazole works on its own.” Not supported. The adult trial of mebendazole alone stopped for lack of effect, and a pediatric phase 1 of it alone found limited activity.
• “Ivermectin cures cancer.” Unproven. No completed human cancer trial; two immunotherapy combination trials are pending.
• “Fenbendazole cured Joe Tippens.” Overstated. He was on pembrolizumab in a trial at the same time.
• “Case series prove fenbendazole works.” Not supported. The published series was retracted, and every patient had standard therapy too.
• “84% of patients benefit” (2026 cohort). Unproven: 84% of the 122 of 197 who answered a six-month survey, counting stable disease; self-reported, uncontrolled, and under an expression of concern.
• “They are harmless.” Contradicted. Liver injury, low white counts and ivermectin neurotoxicity are documented, the last at approved doses as well as in overdose.
• “No big trial means they do not work.” Not supported. Off-patent drugs rarely get funded trials, and absence of evidence is not evidence of absence.

The idea is reasonable and the drugs are cheap, which is why this deserves serious trials rather than dismissal. Today the human evidence is thin: a modest mebendazole signal as an add-on, open ivermectin trials, and nothing controlled for fenbendazole. If you want to try one, the defensible version is human-grade mebendazole taken with food, added to standard treatment, with your oncologist informed and your labs checked. The two ivermectin trials are listed on ClinicalTrials.gov under NCT07487805 and NCT05318469, and the Society for Integrative Oncology publishes information for patients and care partners.

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References:

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