Fenbendazole (FEN) is a broad-spectrum benzimidazole anthelmintic approved for use in numerous animal species. It has been used extensively in rodent pinworm control experiments.
At our institution, the fenbendazole diet was supplemented with additional vitamins to compensate for loss during autoclaving. This may have accounted for the antitumor effect observed during the treatment.
Efficacy
Fenbendazole (methyl N-(6-phenylsulfanyl-1H-benzimidazole-2-yl) carbamate) is a broad-spectrum benzimidazole anthelmintic that is approved for use in many animal species. It also has a high margin of safety and is well tolerated by experimental animals.7,8 Moreover, fenbendazole is known to have moderate microtubule depolymerizing activity and has antitumor effects in in vitro and in vivo experiments.
It has been shown that fenbendazole is effective against the nematode Trichinella spp. infected mice, resulting in significant reductions of muscle larvae. It has also been reported that fenbendazole is efficacious against cestodes, including Mesocestoides spp. tetrathyridial infection, and trematodes such as Heterobilharzia americana and Nanophyetus salmincola.
To evaluate whether fenben lab fenbendazol and vitamins can prevent the growth of human lymphoma xenografts in SCID mice, diets supplemented with fenbendazole, a control, or both fenbendazole and vitamin C were fed to 4-wk-old SCID mice that had been implanted subcutaneously with 3 x 107 lymphoma cells. Tumor growth was measured at 4-d intervals until the tumor reached a predetermined volume. Initial and terminal total white cell counts and neutrophil and lymphocyte counts did not differ among the 4 groups. However, the fenbendazole group showed a significantly reduced tumor size compared to the vitamin C alone.
Safety
Fenbendazole (methyl N-(6-phenylsulfanyl-1H-benzimidazole-2-yl) carbamate) is a broad-spectrum benzimidazole anthelmintic that is well-tolerated in a wide variety of animal species. It has moderate microtubule depolymerizing activity and a potent antitumor effect in human cancer cells.7
Achieving control of pinworm infections at research facilities requires a robust combination of disinfection procedures and quarantine protocols to prevent movement between and within institutions. However, these efforts are frequently thwarted by nonvigorous use of diagnostics, contaminated dietary ingredients, or sharing of mice between laboratories and institutions.
Ring-necked pheasants raised on propagation farms are often severely parasitized with Syngamus trachea. This parasite causes significant economic loss due to reduced egg production, affecting the profitability of commercial hatcheries. A benzimidazole-class anthelmintic, fenbendazole, has been shown to be effective in controlling these parasites. Moreover, fenbendazole has been shown to have a relatively wide margin of safety in young pheasants. In this study, a feed-based dose of 100 ppm fenbendazole was administered to young pheasants for 7 days.
Dosage
In addition to its antihelminthic actions, fenbendazole inhibits cell growth in parasites by binding to -tubulin, thereby blocking the polymerization of tubulin dimers into microtubules. Additionally, it has been shown to inhibit glucose absorption in cancer cells, which enables the tumors to grow rapidly by utilizing the energy from glycolysis (Warburg effect).
Studies at Cornell College of Veterinary Medicine showed that fenbendazole is effective against Giardia and various intestinal helminth infections in dogs. It has also been used successfully in cats to treat pulmonary helminths and lungworms.
During an 8-wk facility treatment with a fenbendazole diet at our institution, human lymphoma xenografts did not grow in C.B-17/Icr-Prkdcscid/Crl (SCID) mice, a model that usually yields 80% to 100% successful tumor growth within 21 d. Initial complete blood counts did not differ between treatment and control groups, indicating that the fenbendazole diet caused a leukocyte response consisting primarily of neutrophils. At study termination, all groups had significantly fewer total white cell and neutrophil responses than did the control group.
Side Effects
Fenbendazole has been shown to interfere with cancer cells’ ability to take in glucose, a crucial process for cell division. This has led to a significant decrease in the number of cancer cells both in laboratory tests and in live animals.
The anthelmintic properties of fenbendazole have been demonstrated against a variety of intestinal and pulmonary helminths. It is particularly useful for treating the trematode Giardia in dogs.
It also appears to be effective in reducing the frequency of Aspiculuris tetraptera and Syphacia spp. infestations in research rodent facilities. However, infestations continue to occur despite the use of fenbendazole-medicated diets, nonvigorous decontamination procedures, and sharing of animals between facilities.
The avian gastrointestinal worms Platynosomum fastosum and Heterobilharzia americana are also susceptible to fenbendazole. The drug should not be used concurrently with the bromsalan flukicides, as they may produce serious adverse reactions in some avian species. It also should not be used with praziquantel, since it increases fenbendazole concentration and delays conversion to the sulfoxide and sulfone metabolites.