In January 2025, Mel Gibson told the influential podcaster Joe Rogan that three of his friends who previously had Stage 4 cancer no longer had cancer “at all.”
They had been cured by the antiparasitic drugs ivermectin and fenbendazole, Mr. Gibson claimed on an episode of “The Joe Rogan Experience” that has been viewed on YouTube more than 13 million times.
There is no high-quality evidence that ivermectin has any benefit for cancer patients. Fenbendazole is not approved for human use. Still, in the months after that episode aired, prescriptions for these drugs jumped significantly, according to research published Tuesday in JAMA Network Open. The highest prescription rates were among men, white patients and those in the U.S. South.
The increase was especially pronounced among cancer patients: The rate of prescriptions from January through July 2025 more than doubled compared with the same window the year before. Oncologists said they worried their patients may delay or forego effective therapies while turning to these unproven treatments.
The findings reflect the complex landscape in which medical decisions are now made. Patients can readily find health information — both accurate and inaccurate — on social media, in podcasts and from A.I. chatbots. A recent report from the Pew Research Center found that half of U.S. adults under 50 get health and wellness information from influencers or podcasters, many of whom are not health professionals.
When those sources share health misinformation, it can quickly spread, said Michelle Rockwell, an assistant professor of family and community medicine at the Virginia Tech Carilion School of Medicine and an author of the paper. Dr. Rockwell previously studied the increase in ivermectin and hydroxychloroquine use during the Covid-19 pandemic.
Cancer patients can be especially vulnerable to misinformation, said Dr. Shikha Jain, an oncologist at the University of Illinois Cancer Center.
“There’s this perfect storm of fear, urgency, uncertainty, information overload and then this desperate need for hope,” Dr. Jain said. “When somebody is offering you a magic cure for something and they give anecdotal examples, it can feel very hopeful.”
The study looked at patients who were prescribed ivermectin and a benzimidazole, a class of drugs that includes fenbendazole, on the same day. It was not designed to show that Mr. Gibson’s remarks directly caused the increase in prescriptions.
Overall, the prescription rate for the combination of ivermectin and benzimidazole was still very low, about four per 100,000 patients over the first seven months of 2025. Still, Dr. Rockwell said she was struck by “just how fast it feels like the rise happened.”
Oncologists say patients increasingly come to them asking for these drugs after hearing about them from friends or reading about them online.
Ivermectin in particular is “a very good example” of how health misinformation can spread, Dr. Jain said. It’s a real medication that has been approved by the Food and Drug Administration to treat parasitic infections, head lice and rosacea. There have been some preclinical studies involving animals and cells in petri dishes that have hinted at an anticancer benefit, and a handful of clinical trials are testing it in combination with immunotherapy for cancer.
And it’s easy for compelling stories about it to spread online or by word of mouth.
“I always tell my patients, we are not mice. And anecdotal data of one or two patients is not proof,” said Dr. Eleonora Teplinsky, an oncologist at Valley Health System in New Jersey who studies cancer misinformation.
Many medications show promise in the preclinical phase, said Dr. Skyler Johnson, a radiation oncologist at the University of Utah Huntsman Cancer Institute. “And then we put these drugs in human clinical trials and the vast majority of the time, greater than 90 percent of the time, these medications don’t seem to either benefit patients or don’t seem to be safe for patients,” he said.
Dr. Johnson said that he tells patients who ask about ivermectin that it may work in cancer cells in mice, but that at high doses it could be toxic in humans. It could also interfere with conventional cancer treatments, making them less effective or more toxic. In an effort to reassure and build trust with his patients, he said, he also tells them that he would recommend the drug if it was ever proven to be safe and effective for cancer.
Until then, though, “I don’t prescribe it and I don’t recommend physicians prescribe it,” he said.
Dr. John Mafi, a primary care physician and researcher at the University of California, Los Angeles, and the senior author of the new study, said it wasn’t able to answer an essential question: Who is prescribing these medications to cancer patients?
It also did not look at how the patients taking these drugs fared, or what other therapies they were taking.
Dr. Johnson has published research showing that patients who used alternative medicine in lieu of conventional cancer treatment were at a significantly increased risk of death compared with those who received standard care.
Doctors said they had seen patients who decided to take ivermectin regardless of their advice. Some never came back, but others returned months later, when their cancer had worsened.
“By the time they get to us, their cancer has progressed, and they are no longer curable,” Dr. Jain said. “Or they start off with metastatic disease, they take these medications and then by the time they get to us they are too sick to get treatment at all.”
Nina Agrawal is a Times health reporter.
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