Ivermectin, Mebendazole & Fenbendazole to Treat Cancer - Quick Reference Sheet
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Ivermectin, Mebendazole & Fenbendazole to Treat Cancer

Created on 08/10/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 5 – Audit

Decades-old anti-worm medicines that kill cancer cells in the laboratory and shrink tumours in animals; carry-over to people has not been shown. Liver injury is the main harm, sometimes severe, detectable in blood tests. Alongside standard care, with the treating team informed: a modest chance of unproven benefit against a real but detectable risk. Instead of proven treatment, clearly unfavourable. (Full Review)

Protocol

Trial-derived mebendazole dosing (Riggins and Gallia, Johns Hopkins)
25–200 mg/kg/day by mouth
Alongside alkylating chemotherapy given after radiotherapy; 200 mg/kg/day carried forward as tolerable.
Lay protocol dosing (Makis-type regimen)
Ivermectin 1.0–2.0 mg/kg/day with mebendazole 1000–1500 mg/day
Or fenbendazole 444–1000 mg/day; 6 days on, 1 day off, minimum three months. An order of magnitude above the licensed anti-parasite doses.
Best time of day
With the largest fat-containing meal
Evening administration commonly preferred; where doses are split, morning and evening with food.
Time to effect
Time to effect
Not established
No trial has demonstrated an effect to time.
First assessment
8–12 weeks
Same imaging and tumour markers as at baseline; the convention drawn from trial and protocol design.
Intended duration
Minimum three months
Lay protocols specify a minimum of three months, with continuation conditional on response; not lifelong interventions.

Benefits

Contraindications
  • Metronidazole with mebendazole
  • Pregnancy (particularly the first trimester) and breastfeeding
  • Child-Pugh Class B or C liver impairment, or baseline liver enzymes above three times the upper limit of normal
  • Neutrophil count below 1.0 × 10⁹/L
  • Known Loa loa co-infection, or residence where loiasis is endemic
  • Children under 15 kg
  • Active seizures or extensive brain metastases (ivermectin above the licensed dose)
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Key Interactions
  • CYP3A4 inhibitors (azole antifungals, macrolide antibiotics, ritonavir, grapefruit juice)
  • CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, phenobarbital, St John's wort)
  • P-glycoprotein inhibitors (verapamil, quinidine, ciclosporin, quercetin, curcumin with piperine, cannabidiol)
  • Cimetidine
  • Other liver-toxic agents (paracetamol/acetaminophen at or near maximum dose, methotrexate, isoniazid, high-dose niacin, anabolic steroids, kava, high-dose green tea extract, regular alcohol)
  • Immune checkpoint inhibitors (pembrolizumab, nivolumab, balstilimab)
  • Warfarin
  • Supplements with additive effects (high-dose curcumin, epigallocatechin gallate, berberine, dichloroacetate, high-dose vitamin E, cannabidiol)
    •

Risk & Side Effects

  • High: Drug-induced liver injury; gastrointestinal effects
    •
  • Medium: Ivermectin neurotoxicity at doses above the licensed range; bone marrow suppression; substitution for or delay of effective treatment; product quality and dosing errors from veterinary formulations
    •
  • Low: Severe skin reactions; interaction-driven toxicity; reproductive and developmental toxicity
    •
  • Speculative: Interference with immune therapy response; long-term consequences of continuous tubulin inhibition
    •

Monitoring

Marker Target Why
Alanine aminotransferase < 25 U/L (men), < 20 U/L (women) Earliest, most sensitive sign of liver-cell injury
Aspartate aminotransferase < 25 U/L Confirms liver-cell injury and, with the above, separates it from muscle origin
Alkaline phosphatase 40–90 U/L Detects the bile-flow pattern of injury reported with fenbendazole
Gamma-glutamyl transferase < 25 U/L (men), < 20 U/L (women) Sensitive marker of bile-duct irritation and of alcohol contribution
Total bilirubin 0.3–1.0 mg/dL Marks loss of liver function rather than mere enzyme leakage; the key severity signal
Albumin 4.2–5.0 g/dL Reflects the liver's manufacturing function and sets the free, active drug fraction
Neutrophil count 2.0–5.0 × 10⁹/L Detects the marrow suppression seen with prolonged high-dose benzimidazoles
Lymphocyte count 1.5–3.0 × 10⁹/L A decreased count was the most common adverse event in the children's trial
Lactate dehydrogenase 140–180 U/L Non-specific marker of tumour burden and cell turnover, useful as a trend
High-sensitivity C-reactive protein < 1.0 mg/L Tracks the inflammatory component of disease activity and flags intercurrent infection
Disease-specific tumour marker Below the assay's reference threshold, or falling from baseline The only routinely available quantitative signal of disease response between scans
Creatinine and estimated filtration rate Estimated filtration rate > 90 mL/min/1.73 m² Establishes clearance capacity and detects dehydration from gastrointestinal effects

Cadence: Baseline panel within two weeks of starting, with imaging and tumour markers; liver enzymes and blood count at 2 weeks and 4 weeks, then every 4–8 weeks for the first 6 months, then every 3 months; an immediate unscheduled panel at any new fatigue, yellowing, dark urine, right-upper-abdominal pain, fever, or neurological symptom; imaging and tumour markers repeat at 8–12 weeks.

Qualitative Assessment

  • Energy and functional capacity — the most common first complaint in reported liver-injury cases
  • Appetite and nausea — dose-dependent and the usual reason for dose reduction
  • Mental clarity, balance, and vision — early warning signs from the brain on ivermectin
  • Sleep quality — broken sleep or heavy daytime drowsiness can precede more obvious neurological effects
  • Skin and mouth — any spreading rash, particularly with mouth or eye involvement
  • Urine colour and yellowing of the skin or the whites of the eyes — the visible signs of the highest-severity risk
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.