Fenbendazole is a common antihelminthic drug, typically prescribed by veterinarians to treat intestinal parasites such as roundworms, hookworms, whipworms and lungworms. It is also used to deworm dogs. But in a series of videos posted on Facebook and TikTok, a veterinarian in British Columbia claims that the dog dewormer cures cancer, prompting many to wonder if it really does work.

The answer is no, at least not as a stand-alone treatment for cancer. Nevertheless, the drug might have potential for use in combination with chemotherapy. Chemotherapy is a blunt instrument that floods the body with poisonous chemicals, killing cells that are either cancerous or fast-growing. It’s a useful tool, but it can also harm normal cells that are regenerating at a fast rate to replace damaged ones and that are essential for survival. It is for this reason that doctors must walk a fine line when prescribing chemo. Too much chemo and it can kill the patient; too little and it can fail to eliminate the cancer.

A new study shows that a simple, cheap alternative medicine may help to enhance the effectiveness of a commonly used chemotherapeutic agent. The drug, fenbendazole, is an antihelminthic that’s effective against multiple types of parasites and works by disrupting the tubulin microtubule equilibrium. This causes the parasites to lose their ability to form a spindle to propel them through cell division, causing them to die. Febendazole has also been found to inhibit the formation of new blood vessels in tumors, suggesting that it could be helpful in delivering other drugs such as chemotherapy agents or targeted therapies.

In this study, EMT6 tumors were treated with three daily injections of fenbendazole (50 mg/kg/day, i.p.) or with 10 Gy of x-ray radiation. The growth curves of the unirradiated tumors were indistinguishable from control data, but irradiation significantly inhibited the growth of all treated tumors. Intensive treatments of fenbendazole were toxic to the cells and increased the sensitivity of the cells to radiation. However, fenbendazole did not alter the dose-response curves for radiation or docetaxel, which suggests that the drug does not potentiate the antineoplastic effects of these agents.

In experiments to determine the effect of fenbendazole on radiation cytotoxicity, cultures were made hypoxic by sealing in glass pressure bottles with rubber gaskets and inserting needles for influx and efflux of gases, then treated with vehicle or fenbendazole, sealed again and transported to the irradiator. After irradiation, the cultures were opened and the number of surviving cells counted using clonogenicity assays. The results show that 2-h treatments of fenbendazole and severe hypoxia were particularly toxic, with a significant reduction in the yield-corrected surviving fractions. However, the surviving fractions for oxygen-treated cells were not significantly lower than those of nonirradiated controls. Therefore, the fenbendazole-oxygen interaction did not reduce the effective dose of radiation. fenbendazole cures cancer