At least once a week, someone asks Dr. Skyler Johnson if ivermectin can treat their cancer.
Patients have asked about the anti-parasitic drug for years, especially during the pandemic. But in recent months, Dr. Johnson, a radiation oncologist at the University of Utah Huntsman Cancer Institute, has fielded more and more questions about the medication.
Exaggerated and inaccurate comments about ivermectin have intensified online lately. Google searches for “ivermectin” hit their highest point in January since a Covid wave in 2022. That month, the actor Mel Gibson appeared on the hit podcast “The Joe Rogan Experience” and said that three friends with Stage 4 cancer recovered after taking ivermectin, among other drugs. Researchers said the podcast, which received 10 million views on YouTube alone, fed into a flood of inaccurate claims and misinformation about the drug’s purported health benefits.
At the same time, politicians in several states are promoting legislation that would make it easier for people to obtain ivermectin. The governor of Arkansas signed a bill last week that would enable people to buy it without a prescription. Lawmakers in Georgia, Texas, West Virginia, Alabama, Louisiana and Kentucky have filed, or said they plan to file, similar legislation.
A wealth of research has shown the drug does not treat Covid. And there is not evidence to support people taking ivermectin to treat cancer.
“I understand that people, a lot of times, want to take health into their own hands — they want to figure things out on their own,” said Krissy Lunz Trujillo, an assistant professor of political science at the University of South Carolina who researches health misinformation. “But that might have really serious consequences.”
Dr. Johnson worries that people will forgo traditional cancer treatments for a drug that hasn’t been proven to work. He tells patients that there is no rigorous research showing the anti-parasitic drug cures cancer in humans. Still, he has seen some people with early, treatable tumors turn to the drug, and return months later with cancers that have spread to their lymph nodes, bones and brain.
“These are really the cases that keep people up at night,” he said.
What Ivermectin Can and Can’t Do
Scientists do not dispute that ivermectin is powerfully effective — against parasites. The drug was such a breakthrough in the fight against tropical parasitic diseases that two scientists who studied it won the Nobel Prize in 2015.
The Food and Drug Administration has approved ivermectin tablets to treat certain parasitic infections, and the agency has authorized ivermectin lotions to kill lice and creams to help with rosacea. Veterinarians also use the drug to prevent and treat parasitic diseases in animals.
The drug seems to have no benefit when it comes to treating Covid. Large clinical trials have shown that ivermectin did not help patients recover from an infection faster than a placebo, nor did it reduce the risk of hospitalization.
Scientists are, however, conducting early research into ivermectin and cancer.
“It’s certainly not a cancer breakthrough, from what we can tell,” said Dr. Larry Norton, medical director of the Evelyn H. Lauder Breast Center at Memorial Sloan Kettering Cancer Center. “But it’s being actively investigated. That’s really all that one can say at this point.”
Studies in human cells suggest that the drug may kill certain types of cancer cells in a way that triggers the immune system, said Dr. Peter P. Lee, chair of the department of immuno-oncology at Beckman Research Institute of City of Hope in Duarte, Calif. In mouse studies, Dr. Lee has seen that the drug, on its own, does not shrink breast tumors. But it’s possible that the drug may have benefits for breast cancer when used alongside existing cancer immunotherapy, he said. Researchers are studying a combination of ivermectin and an investigational cancer drug in people with breast cancer.
While some inaccurate social media posts claim that ivermectin can treat cancer because tumors themselves are parasitic, the promise of ivermectin for cancer has nothing to do with its anti-parasitic effect, Dr. Lee said. Rather, it seems that the drug may be able to modulate a signal involved with cancer growth.
But doctors still need larger, randomized clinical trials to better understand whether ivermectin could treat cancer. Just because a drug seems to work in animals doesn’t mean those results will translate into real-world outcomes, Dr. Johnson noted. There are “hundreds of medications that look to be promising in a preclinical setting” every year, he said, adding, “The vast majority of those will never be shown to be effective in humans.”
The Risks of Misuse
Doctors generally view ivermectin as safe at the doses prescribed to treat parasitic infections. But many expressed alarm at the idea that patients would take the drug for unproven purposes.
“If there’s no benefit, then you only have risk,” said Dr. David Boulware, an infectious disease physician at the University of Minnesota who has studied ivermectin and Covid.
Dr. Johnson said that beyond his concerns about people setting aside effective cancer medications in favor of ivermectin, he is also concerned about people taking ivermectin alongside traditional treatments. This is because the medication may affect the way people metabolize other drugs, he said. Ivermectin can also interact with blood thinners.
In high doses, ivermectin can be toxic and cause central nervous system problems like blurred vision, confusion and seizures, especially in children, said Dr. Susanna Naggie, a professor of medicine at Duke University who has studied ivermectin and Covid. The F.D.A. has also warned that high doses can lead to coma or even death.
And doctors don’t yet know the risks of taking ivermectin routinely or over a long period of time, said Dr. Daniel Kuritzkes, chief of the division of infectious diseases at Brigham and Women’s Hospital in Boston.
That’s one reason that he and other doctors are so concerned about the prospect of the medication becoming more widely available.
The idea that people can “just walk in and take, and take at whatever dose that they believe, or can find somewhere online that they think might work,” with no monitoring from a health care provider, would be “dangerous,” Dr. Naggie said.
