Prescriptions of ivermectin for cancer patients doubled in just seven months, a new study has found, prompting urgent warnings from oncologists and charities about the dangers of abandoning proven treatments for an unlicensed anti-parasitic drug.
Sharp rise in off-label use
Research published in JAMA Network Open revealed that the number of cancer patients receiving ivermectin rose by more than 2.5 times between 1 January and 31 July 2025, compared with the same period in 2024. Overall prescriptions of the drug – including for non-cancer patients – also more than doubled over that time.
The study analysed de-identified electronic health records from more than 68 million patients across 67 health systems in the United States. It found that the increase was concentrated among White patients, men, and those living in the southern states – demographic patterns that closely match the known audience of a popular podcast that promoted the drug as a cancer cure.
Celebrity endorsement fuelled demand
The catalyst appears to have been an episode of The Joe Rogan Experience aired on 9 January 2025, in which actor Mel Gibson told the host that three of his friends with stage IV cancer had been cured by taking ivermectin alongside a benzimidazole compound, a type of substance found in agricultural chemicals.
According to the study’s authors – Drs Michelle S. Rockwell, Katherine L. Kahn and A. Mark Fendrick – the podcast episode was “viewed by more than 60 million individuals across multiple platforms”. They noted that the demographic and regional patterns of prescribing “mirror the audience characteristics of the podcasts and media platforms promoting these regimens, suggesting selective amplification and reach of health misinformation”.
The study, titled Ivermectin-Benzimidazole Prescribing Following Celebrity Endorsement, also highlighted a broader concern: “The elevated prescribing observed among patients with cancer is particularly concerning; individuals facing life-threatening illness may delay or forgo conventional treatments in favor of unproven therapies, potentially allowing their disease to progress.”
No proof ivermectin works against cancer – and real risks
Ivermectin is an anti-parasitic medication approved by the US Food and Drug Administration for treating specific infections such as river blindness and threadworms, and is widely used in veterinary medicine. It gained notoriety during the Covid-19 pandemic when it was promoted by vaccine sceptics as an alternative treatment – a position later echoed by Robert F. Kennedy Jr., now Secretary of Health and Human Services, on his own podcast before he joined the White House.
Despite its widespread public profile, there is no robust clinical trial evidence that ivermectin is safe or effective for treating cancer in humans. The authors of the study, along with multiple medical organisations, stress that cancer is not a parasitic infection but a mutation of cells, and that the drug has no proven medicinal properties beyond its original use.
Richard Simcock, chief medical officer at Macmillan Cancer Support, said in a press release: “There is currently zero real-world clinical evidence that it might be helpful in the treatment of cancer. And yet, with just a few clicks on X and Instagram, I was astounded by the sheer number of people professing ivermectin’s benefits for cancer treatment and even trying to find ways to buy it.”
Laboratory studies have shown that ivermectin and benzimidazole derivatives can inhibit the growth of cancer cells in a dish or in animals, and may induce cell death. Some of these studies examined the effect of the drugs alongside conventional treatments. However, Simcock emphasised that such results cannot be directly replicated in humans. The American Cancer Society has similarly stated that the claims are based on “limited, early studies that cannot be directly replicated in humans”. Even the more promising laboratory tests used ivermectin in combination with existing cancer drugs – never alone.
A small study involving nine patients with metastatic breast cancer found no evidence of benefit when ivermectin was added to their treatment regimen. Meanwhile, high doses of the drug can cause serious neurological side effects, including seizures, confusion, coma and even death. It can also provoke nausea, vomiting and diarrhoea – symptoms that may worsen the discomfort already experienced by cancer patients. There is also a risk of harmful interactions with conventional chemotherapy drugs.
“The disinformation often stems from the misinterpretation of early laboratory findings,” Simcock explained. “What works in a petri dish does not automatically translate to a human body, especially when the doses required would be toxic.”
Benzimidazoles as a class have been investigated for anti-cancer properties because of their ability to disrupt microtubule formation, a process needed for cell division. Some benzimidazole derivatives, such as bendamustine, are approved for treating certain blood cancers. But the specific combination of ivermectin with benzimidazoles promoted by celebrities has never been validated in clinical trials.
The study authors noted that even the National Cancer Institute in the US is conducting preclinical research into ivermectin’s potential anti-tumour effects, but oncologists caution that such work is preliminary and does not confirm human effectiveness. Some NCI scientists have reportedly expressed concern that funding is being diverted from more promising avenues of research.
Macmillan’s Simcock said the trend reflected a dangerous shift: “Some patients are rejecting evidence-based cancer drugs in favour of non-evidence-based parasitic drugs. That is not a choice based on science – it is a choice based on misinformation.”
Ivermectin remains unregulated by the FDA for any use beyond the treatment of parasitic infections. The American Medical Association has formally opposed its off-label use for cancer. And the study’s authors warned that the very nature of the demographic spread suggests the misinformation is being deliberately amplified to those most likely to follow it.