Fenbendazole is an anthelmintic agent used against gastrointestinal parasites such as pinworms, giardia, roundworms, hookworms, whipworms, and the tapeworm genus Taenia. It has also been shown to have antitumor activity in cells and mice. It acts by blocking the polymerization of microtubules, which are essential for cell division and chromosome separation.


Fenbendazole is a broad-spectrum benzimidazole anthelmintic that is approved for use in numerous animal species. It is known to have a high safety margin and most animals tolerate it very well. Its exclusive action as an anthelmintic is related to its binding to b-tubulin, which destroys the function of microtubules and causes cell detachment. The drug is also known to interfere with cell division by inhibiting the formation of microtubules and preventing chromosome separation. It has been proposed that fenbendazole may be useful in treating some cancers because it can affect the growth of cancer cells.

It is a popular veterinary medication for intestinal helminth parasites in cats and dogs. It is effective against hookworms, whipworms, lungworms, and tapeworms. It is also used to treat Giardia and nematodes in dogs and horses. It is available in granules or as a liquid suspension and is administered orally. It should be stored at room temperature and kept away from sunlight.

In addition to its antiparasitic effects, fenbendazole has been shown to have anti-tumor properties in vitro and in vivo. In an experiment, 2-h and 24-h treatments of fenbendazole caused significant decreases in cell numbers in EMT6 monolayer cultures. Moreover, the drug was not toxic to aerobic EMT6 cells at doses that approached the limit of solubility.

These results are consistent with the results of a previous experiment, which showed that three daily i.p. injections of fenbendazole did not alter tumor volume in mice irradiated with the fenbendazole-containing antihelminthic diet. In this experiment, mice were stratified by tumor volume at the time of treatment and the time to four-fold volume was measured.

It is important to note that this method of administration of fenbendazole is ‘off label’ for use in cats. While it is safe and well tolerated by most cats, it is important to follow the instructions of your veterinarian very carefully. This medication is available in a granule form and as a liquid suspension, which must be mixed with water and given orally. Liquid forms must be measured very carefully to prevent gastrointestinal upset.

Methyl 5-(Phenylthio)-2-benzimidazolecarbamate

Fenbendazole is a broad-spectrum, benzimidazole anthelmintic with a high deworming effect in various animals. Its action is based on its binding to b-tubulin microtubule subunits, disrupting their polymerization and thereby detaching parasites from the host cells (Correa, 1999). Fenbendazole is also reported to have antitumor effects by inhibiting tubulin polymerization and blocking the formation of mitotic spindles in cancer cells.

A 2021 study published in Scientific Reports showed that fenbendazole, along with mebendazole and albendazole, significantly reduced pancreatic cancer cell proliferation in vitro. However, the effect was not seen in vivo, where the drug had little or no effect on tumor growth. Other studies have shown that fenbendazole reduces the growth of human breast cancer cells and may be a radiosensitizer for other types of cancer, including colorectal and prostate cancers.

Another use of fenbendazole is to treat carnivorous raptors with serious infections of Oster nematode, Cooper nematode, sawthorn nematode and trematodes. It has a high efficacy against these worms and can be administered orally at a dose of 10 mg/kg. It can also be used in dogs and cats to treat gastrointestinal helminths, such as whipworms and hookworms.

The pharmacology of fenbendazole is not well understood. It is believed that it binds to glycine and arginine residues in the mitochondrial inner membrane, inhibiting oxidative phosphorylation. This inhibits ATP production and leads to cell death. It also prevents lipid accumulation and inhibits the activation of certain proteins. It is absorbed well after oral administration. The drug is generally well-tolerated, except for an occasional gastrointestinal upset due to the release of antigens by dead parasites.

Recently, a patient with advanced nonsmall cell lung cancer received fenbendazole as part of her pembrolizumab treatment. She developed severe liver dysfunction 9 months later. Her family revealed that she had been self-administering fenbendazole for a month, solely based on social media reports suggesting its effectiveness against cancer. Her hepatotoxicity resolved when she stopped self-administering fenbendazole.


Fenbendazole (methyl N-(6-phenylsulfanyl-1H-benzimidazol-2-yl) carbamate) is a benzimidazole compound with broad antiparasitic activity used in various animals. It is thought to exert its anthelmintic effects by binding to b-tubulin microtubule subunits and disrupting their polymerization. Recently, it has been shown to have antitumor activities in human cancer cells.

In one study, fenbendazole inhibited the growth of EMT6 tumors in BALB/c mice. Tumor volumes were measured three times per week from the time each tumor became palpable until it reached a volume of 1000 mm3. Mice were then stratified by tumor volume and irradiated or treated with fenbendazole. The irradiated and unirradiated groups were then compared to determine whether fenbendazole could significantly reduce tumor growth. The results of this study showed that irradiation did not affect the effect of fenbendazole. In addition, fenbendazole did not alter the growth of unirradiated tumors.

Another study examined the effect of fenbendazole on cell viability in human cancer cells. The cells were cultured in the presence of varying concentrations of the drug for 24 and 48 hours. The resulting data were analyzed using AlamarBlue assays. The results of this assay showed that the fenbendazole was cytotoxic to all four of the cancer cells tested, but not to normal human liver and lung cells.

The fenbendazole formulation is currently sold as a medicated drinking water for poultry. It is diluted in the medicator’s tank with water generally in a 1:128 ratio to obtain medicated drinking water having a fenbendazole concentration of from about 45 to about 80 ppm, preferably about 65 ppm. The formulation is also used for medicated water for cows and pigs. The fenbendazole in this formulation is stabilized by the addition of glycerol and methylcellulose, which prevent the fenbendazole from breaking down or dispersing in high temperatures. fenben lab fenbendazol

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