Prescriptions for two antiparasitic drugs, ivermectin and fenbendazole, have recently surged in the US, according to a new study. Originally developed to treat parasitic worms, the drugs are now being discussed online as possible cancer treatments.
In January 2025, Mel Gibson appeared on the Joe Rogan Experience podcast claiming that ivermectin and fenbendazole can treat cancer. He said the drugs cured three friends of stage 4 cancer. Clips from the interview spread rapidly on social media.
For some listeners, the interview was probably convincing enough for them to try and obtain the drugs for themselves. Prescriptions for ivermectin more than doubled among cancer patients after the podcast appearance. Google searches increased sharply and online forums filled with discussions about self-dosing. Within days, the two drugs were being touted online as possible breakthrough cancer therapies.
But what does the scientific evidence actually show?
First, let’s consider ivermectin, a widely prescribed antiparasitic drug, used in both humans and animals. Laboratory studies have found that it can affect several biological processes linked to cancer growth.
One study found that it may interfere with a pathway that helps cancer cells survive. Other research has explored whether ivermectin can make tumours easier for the immune system to detect and destroy.
However, findings from laboratory studies do not automatically translate into successful treatments for patients. So far, no studies have looked at the effectiveness of ivermectin and fenbendazole in cancer patients, but some early-stage trials are now underway.
Fenbendazole belongs to a group of antiparasitic drugs called benzimidazoles. Unlike ivermectin, it is only used in animals and is not approved for human use.
In laboratory studies, fenbendazole has been shown to interfere with cancer in several ways, including disrupting cancer cells’ uptake of glucose (which these cells rely on heavily), impairing how they manage chemical stress, and damaging their structure so they can no longer function properly.
Public interest in fenbendazole increased in 2019 after a US businessman claimed it helped him recover from lung cancer. However, the story often overlooked an important detail: the patient was also receiving experimental cancer treatment and several other drugs at the same time.
Why scientists remain cautious
This leads to the central issue: the quality of the evidence.
Most evidence supporting ivermectin and fenbendazole as cancer treatments comes from studies in cells or animals, not from clinical trials involving patients.
One paper reporting major improvements in three cancer patients taking fenbendazole was later retracted because of concerns about the reliability of the data.
Some supporters also claim that the two drugs may work better when used together because they appear to affect cancer cells in different ways. However, combination therapy of the two antiparasitic drugs taken together have not been conducted.
Future studies must use a combination of the two drugs to either back up or refute Gibson’s claims. Without scientific evidence, it would be dangerous to assume these drugs are a miracle cancer treatment.
Interest in these drugs has grown quickly, and some human trials testing them (alongside conventional treatments) are now underway. But this doesn’t mean ivermectin has been proven to work against cancer. It simply means researchers believe the laboratory evidence is strong enough to justify further study. Human trials, however, are still at an early stage.
Cancer can leave people searching urgently for hope, especially when treatments are expensive, difficult or uncertain. That helps explain why stories about familiar, low-cost drugs can spread rapidly online.
Until large, well-conducted trials are completed, ivermectin and fenbendazole should be considered experimental cancer treatments. For now, medical experts recommend relying on evidence-based cancer treatments supported by clinical research.
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