Fenbendazole (FEN) is a benzimidazole-class anthelmintic that controls internal parasites in domestic food-animal species. It has demonstrated efficacy against nematodes, e.g., Syngamus trachea, in pheasants.
Blood samples were collected from control and fenbendazole-treated mice on the day of treatment and again after 5 days. Initial white cell counts showed a decrease in neutrophils and an increase in lymphocytes.
Safety
Fenbendazole (methyl N-(6-phenylsulfanyl-1H-benzimidazo-2-yl) carbamate) is a broad-spectrum benzimidazole carbamate anthelmintic that has been used for approximately six decades. It is one of the three most commonly used anthelmintics in veterinary medicine, along with metronidazole and albendazole.
Pinworm infestations remain a problem for many animal facilities, even though PCR testing has increased detection and improved decontamination techniques. Infestations may result from poor decontamination procedures, insufficient use of diagnostics, and the sharing of animals between facilities.
This study was conducted to investigate the solubility and content of two commercial fenbendazole powder brands. A simple, robust HPLC method was developed and validated using a fenbendazole analytical standard and samples from different LOT numbers of each brand. 1H and DOSY NMR experiments in DMSO provided useful information about the solubility of these samples and revealed that the brands contain the active drug as well as other, possibly excipient, chemicals. Samples were then tested for their cytotoxicity with the AlamarBlue assay against human cancer cells.
Efficacy
The broad-spectrum benzimidazole carbamate anthelmintic fenbendazole (methyl N-(6-phenylsulfanyl-1H-benzimidazol-2-yl) carbamate) is a well-established treatment for rodent pinworm infections.7 It has also been shown to suppress cancer cell growth due to its moderate microtubule destabilizing activity and by modulating multiple cellular pathways.
However, the potential for fenbendazole to impact immunity must be considered prior to facility-wide treatment to eradicate pinworms in research mice. The effect on immunocompetence could result in a decreased ability to mount a robust immune response to other challenges, which could affect experimental results.
During an 8-wk facility treatment for Aspiculuris tetraptera pinworm infection at our institution, we found that a fenbendazole diet suppressed the growth of an established human lymphoma xenograft in C.B-17/Icr-Prkdcscid/Crl SCID mice. This result was not due to the addition of fenbendazole alone, as a control diet supplemented with additional vitamins failed to inhibit tumor growth. The treatment effects were associated with a reduction in total white cells and neutrophils.
Dosage
Fenbendazole is a broad-spectrum anthelmintic, in the benzimidazole carbamate group, that has been in veterinary and human clinical use for more than 50 years. It is effective against many intestinal helminths and also has activity against cestodes and trematodes (Giardia spp., Heterobilharzia americana, and Nanophyetus salmincola).
It is safe to give this medication to pregnant dogs, though a lower dosage of 11.3 mg/kg body weight should be used. It shouldn’t be given to pet poultry during molting, as this will cause a delay in cell division and death of the parasites.
It has been found to have strong antitumor activity in human cancer patients. It may have this effect in animals, as well. Typically, this medicine is poured over food to minimize nausea and encourage the animal to consume it. Most versions of this medication recommend a weekly schedule for administration. However, this can be adjusted based on the animal’s needs and the veterinarian’s experience.
Storage
Fenbendazole is fat soluble and slowly absorbs into the bloodstream. It is best dissolved in oil (olive, canola or vegetable) before administration. Alternatively it can be mixed with DMSO and absorbed that way. When mixing with DMSO it is important to stir well and make sure it is completely dissolved.
A solitary worm problem in poultry is typically caused by the parasite Capillaria. This is a serious and deadly parasite that causes the wing rot of chickens. Symptoms are difficult to recognize and can be fatal if not treated.
In an extra-label study, fenbendazole was administered at 100 ppm in the feed for seven days to pheasants. Concentrations of fenbendazole sulfone in the rinon, higado and musculos of pheasants were measured after treatment. Results revealed that fenbendazole poses minimal risk to humans after extra-label administration in pheasants and demonstrates a relatively large margin of safety compared to other sulfone antihelmintics. These data can help guide the conservative withdrawal intervals that should follow extra-label drug use in pheasants. fenben lab fenbendazol
