If you have pancreatic cancer that can't be cured, it makes sense that you wouldn't want to miss out on a medication that could help you slow the disease's spread. Treatments approved by the FDA or available through clinical trials can sometimes offer some hope. But you also might come across claims that antiparasitic medicines like ivermectin, fenbendazole, and mebendazole can bring on miraculous cancer-fighting effects.
Often, this takes the form of personal testimonials, typically on sites that are trying to sell these antiparasitic drugs, says Eric Christenson, MD, an oncologist at Johns Hopkins Medicine. These testimonials have a similar hopeful ring — something along the lines of, “My doctor said my cancer was incurable. But I took this antiparasitic drug and now I’m cancer-free.”
This can sound very appealing, Christenson says, when the alternatives are established treatments like chemotherapy that can cause lots of side effects and can only treat, not cure, advanced pancreatic cancer. But there's no scientific proof that antiparasitic drugs treat or cure the disease in people, Christenson says. And these drugs can pose serious risks, especially if you take them without your doctor's knowledge.
Here's what you need to know about antiparasitics such as ivermectin, fenbendazole, and mebendazole: what conditions they’re approved to treat, what cancer research shows, and how to separate fact from fiction online.
What to Know About Antiparasitics
Antiparasitic drugs treat infections caused by parasites, tiny organisms that live on or inside of people and animals. Ivermectin, fenbendazole, and mebendazole are part of a group of antiparasitics called anthelmintics, which treat infections caused by parasitic worms. These drugs have valid medical uses, but they've also sparked attention by being touted as unproven remedies for various health conditions, including pancreatic cancer.
Ivermectin. This drug was first created for animals — think heartworm medicine for dogs — before the FDA approved it for people in tablet form (Stromectol) to treat parasitic infections like river blindness and threadworms. A topical version (Sklice, Soolantra) that goes on skin is a treatment for conditions like head lice, scabies, and rosacea. Ivermectin has been such a game-changer in fighting parasitic disease globally that the two researchers behind it won a Nobel Prize in 2015. In recent years, though, some people have touted it as a cure for conditions for which it is not FDA-approved and for which there is no credible scientific evidence, including COVID-19.
Mebendazole. This chewable tablet (Emverm) treats several types of infections caused by parasitic worms such as roundworms, hookworms, and pinworms. It's not approved to treat other types of health conditions in people.
Fenbendazole. This deworming drug is a capsule (Panacur, Safe-Guard) that treats parasitic infections in animals such as dogs, cattle, goats, and horses. There's no data to show that it's safe and effective for treating any health condition in people, and the FDA hasn't approved it for such uses.
What Cancer Research on Antiparasitics Shows
People who support taking antiparasitics for cancer say that ivermectin can destroy cancer cells. There's a kernel of truth to that, but it's mainly based on lab studies of cancer cells in dishes. "There's a lot of things that will kill cancer cells in a petri dish that don't necessarily translate into good responses" in people, Christenson says.
For instance, a 2025 lab study found that ivermectin combined with an enzyme called recombinant methioninase (rMETase) got rid of human pancreatic cancer cells in a dish. A 2022 study found that ivermectin plus a chemo drug called gemcitabine also showed promise against pancreatic cancer cells in the lab.
But the vast majority of drugs that have shown promise in labs or in mice have fallen flat in clinical trials that test drugs on people, Christenson says. Besides, no clinical trials on ivermectin, fenbendazole, or mebendazole have been done to find out whether they're safe and effective for people with pancreatic cancer.
What little research exists on the use of antiparasitic drugs in people with cancer has looked at the effects of anthelmintics combined with proven cancer treatments — and it's not clear what effect the anthelmintics had on people's outcomes.
For example, a phase 2 clinical trial looked at the effects of ivermectin combined with the immunotherapy medication balstilimab in people with triple-negative breast cancer that had spread. The results showed that the cancer became worse in six people, stayed about the same in one person, and responded somewhat well to the treatment in another person. So, the results weren't promising, and ivermectin's effect on the outcomes was unclear.
Risks of Taking Antiparasitics if You Have Pancreatic Cancer
Taking ivermectin, fenbendazole, and mebendazole while you're getting treatment for pancreatic cancer could make treatment less effective and worsen side effects.
One of Christenson's biggest concerns is the risk of liver damage and inflammation: "If liver toxicity becomes severe, then people can get high bilirubin [a yellowish pigment in liver bile], which can lead to yellowing skin and itchiness. That's thankfully relatively rare with ivermectin. With fenbendazole and mebendazole, that's certainly more of a concern."
The three drugs have other possible side effects, too. Ivermectin can cause nausea, vomiting, and diarrhea. Taking large amounts cause seizures, a coma, and death.
Mebendazole can cause gut symptoms, allergic reactions, infections, and skin changes that include blistering, peeling, and loosening.
With fenbendazole, simply taking a drug that's meant only for animals isn't safe; animal drugs can be highly concentrated or have inactive ingredients that haven't been tested for use in human medicine.
Always talk with your oncologist if you're thinking about trying an antiparasitic drug. Taking these drugs could have consequences beyond direct impacts on your health. Taking ivermectin for pancreatic cancer, for example, could get you disqualified from joining a clinical trial, which could limit your treatment options.
Despite the risks of taking antiparasitic drugs, some people with pancreatic cancer try them anyway. Christenson never encourages his own patients to take antiparasitics, but he says he'd rather know about it if they do, so he can watch closely for serious concerns like liver inflammation or medication interactions.
"Certainly, I've had a number of patients that have tried it unsuccessfully," he says. For patients who've exhausted standard options and aren't eligible for trials, he takes a candid approach. He tells them: "I really don't agree with this. I've had patients have toxicity with these [drugs] before. But that being said, I'm not really offering you anything great. So I do appreciate why you want to try those."
Tips on Spotting Medical Misinformation
Faulty information about cancer and its treatments spreads fast in the internet age. You might run into exciting claims about supposed miracle drugs or cures through online search results, direct-to-consumer drug ads, personal stories on social media, and viral podcast clips.
If a claim seems too good to be true, you can start by asking your oncologist about it. You also can do your own research online with more confidence by choosing trustworthy health information websites. Look for sites that draw from peer-reviewed scientific studies in journals, established medical experts, and other reputable health sites.
You also can learn how to spot possible signs of misinformation online. Some red flags to watch out for are:
Sensational claims. Be highly suspicious of sites or products that make claims about scientific breakthroughs, miracle cures, secret ingredients, or ancient remedies. Also be wary of any product that claims to cure a variety of illnesses.
Info that's personal rather than scientific. Personal stories in which someone talks about doing well on an unproven cancer treatment can be exciting, but most often they lack any scientific basis and provide false hope. These personal accounts can take the form of blogs, testimonials, and anecdotal reports. They're not based on research, and they could include inaccurate, misleading, or bogus info. Even in the unlikely event that an unproven treatment had some benefit for one person, that doesn't mean it would be safe or effective for most people.
Sponsored search engine results. These links usually show up at the top of your search results, often in a different color or formatting. Some may have helpful info, but others may be attempting to sell you a product for profit.
Sites that claim to offer medical advice. A legitimate health site usually includes a message that its content is meant for information, not medical advice. Only a health care professional who has firsthand knowledge about your health and medical history can give you tailored advice.
No "About Us" section. Legitimate health websites usually include an easy-to-find page that explains who runs it and provides its information.
No medical reviewers listed. Medical reviewers are health care professionals who fact-check the health information in articles to make sure it's accurate and reasonably up to date. Information on cancer and its treatments changes fast. So if the information hasn't been reviewed or updated within a couple of years, it's best to check another site for info that's more recent.
No mention of treatment side effects. All treatments can cause side effects. If none are listed in an article, that could be another red flag.
