Anti-parasitic medications and ovarian cancer

In the past few years, there have been numerous claims that anti-parasitic medications such as ivermectin, mebendazole and fenbendazole can possibly be used against cancer. Here, we take a look at the most recent evidence.

This page covers:

• What are anti-parasitic drugs?
• Recent news and updates
• Ivermectin
• Mebendazole
• Fenbendazole
• Ways to reduce cancer risk

What are anti-parasitic drugs?

Drugs such as Ivermectin, mebendazole and fenbendazole are drugs that have been used for many years in humans or in animals to kill parasites, such as different types of worms.

What is being reported?

It’s been reported online that these drugs can be used by people with cancer to treat their disease.

Why is this being reported?

There have been studies that show that these kinds of drugs can have an effect on cancer cells in the laboratory, causing them to die or stopping them from growing.

This is great news, right?

Not quite.

Using a drug originally found to be effective for one disease, to solve a different problem, is an important area to explore. For example, aspirin was originally used as a painkiller and blood thinner. It is now recommended that some high-risk groups to take a low dose of aspirin regularly (under their doctor’s supervision) as it has been found to reduce the risk of bowel cancer1.

But every drug does need to be tested properly to make sure it does what is being claimed, and it’s safe in the doses needed to treat that disease.

With anti-parasitic drugs such as ivermectin, mebendazole and fenbendazole, we must remember that most of the promising results come from laboratory studies on animals and lab-grown cells - not in real patients.

There is a big difference between being able to kill or slow the growth of cancer cells in a Petri dish and doing the same safely in a human body.,

The research done on these drugs varies, so we’ve briefly summarised below how far research has gotten with each one:

Ivermectin

Ivermectin is a drug used in humans to treat some internal parasites like worms, and external parasites such as head lice.

It has been found in some lab studies to slow the growth of cancer cells and cause them to die.

There haven’t been any large-scale studies into whether it would be effective in humans to treat cancer, and there are worries that the doses it’s thought would be needed to have the desired effect are larger than would be safe to take as a human.

Research continued, but currently there is a lack of data on whether ivermectin is safe for use against gynaecological cancers (including ovarian), or whether it has a positive effect against these cancers.

Mebendazole

Mebendazole is an anti-worm medication used in humans.

In laboratory studies using cancer cells and animals, it’s been found to have anti-cancer properties against several types of cancer cells, leading to cancer cell death and slowed growth.

In some early human studies looking at colorectal cancer, patients were found to have better responses to their standard treatment when taken alongside mebendazole2.

Other results have been mixed, with some trials showing no effect on the disease, and some patients’ cancers actually getting worse, quickly, when taking the drug3.

We need more research before we know whether this may be an effective and safe option to treat cancer.

Fenbendazole

Fenbendazole is a dewormer used to treat animals. This drug is not approved for human use in the US or the UK.

Some early research on cells in the lab suggested the drug may stop cancer cells growing, but other research found it may speed up the development of tumours in rats4.

Currently, there’s no data showing it is effective at treating cancer in humans. In summary…

There’s no evidence from large human studies to suggest taking ivermectin, mebendazole or fenbendazole can safely help to treat cancer. Research is ongoing into how they can be used in this way in humans, but for the moment, it’s not advised to take these medications as part of your cancer treatment.

Remember to always be completely honest with your medical team about any supplements or additional medications you do take, as some may interact with your other treatments, including chemotherapy.

There are things that we know can help reduce cancer risk. These include:

• Eating plenty of fruits and vegetables
• Being physically active
• Maintaining a healthy weight
• Limiting alcohol intake
• Not smoking
• Avoiding processed meat

Ovarian Cancer Action will always ensure we keep up to date and comment on any significant developments in the areas of ovarian cancer prevention and treatment. Cancer Research UK are also a reliable resource. Their comprehensive page on complementary and alternative therapies can help you understand how to find reliable information.

Last reviewed: January 2026