Fenbendazole is the drug of choice for treating pinworm infestation in laboratory rodents. It is also prescribed to cats and dogs for its activity against Giardia spp., a common cause of small bowel diarrhea in these species. Fenbendazole is also a moderate-acting medication for the treatment of intestinal parasites in pet birds, such as parrots, finches and cockatiels.
The anti-parasitic properties of fenbendazole have led to investigation into whether it has other biological activities. Studies have shown that it has immunosuppressive and anti-inflammatory effects. These findings have led to the belief that fenbendazole may be a useful agent for modulating cancer tumor growth and progression in humans as well as in other mammalian species.
A number of experiments were conducted with fenbendazole to determine its cytotoxic effects on human cancer cell lines and its effect on the growth of tumors in mice. In general, the results showed that fenbendazole does not have a significant cytotoxic effect on normal cells. However, it does have an inhibitory effect on tumor cells that grow in the presence of oxygen. It also decreases the proliferation of B lymphocytes. These effects are thought to result from the interference with mitochondrial function in the target cells.
In a study on human cancer cells, fenbendazole was shown to induce the expression of cytochrome p4501A (CYP1A). This enzyme is required for metabolizing fenbendazole, and its increased expression could explain its anti-proliferative effect.
Another study using a mouse model of colon cancer showed that fenbendazole reduced tumor growth and suppressed cellular invasion of the colon. These results are believed to be due to the inhibition of proliferation of cancer cells by a reversible block in signaling pathways necessary for cell cycle control.
Fenbendazole has been shown to reduce the inflammatory response and decrease leukocyte infiltration in the lungs of BALB/c mice exposed to ovalbumin, resulting in lower concentrations of goblet cells in lung sections and fewer eosinophils in the bronchoalveolar lavage fluid. It has been demonstrated that fenbendazole also blocks the activation of CD4+ T cells and prevents the secretion of pro-inflammatory cytokines in vitro.
In a study of the quality of fenbendazole, a quick, robust HPLC method was developed to measure fenbendazole in a variety of samples from two commercial formulations (Brand P and Brand S). This method was validated with the addition of an acetonitrile to the methanol/water mobile phase. NMR and 1H and DOSY NMR experiments confirmed that the HPLC method measures the quantity of fenbendazole specified on the label. In contrast, dissolution studies indicated that both formulations had issues with their ability to dissolve adequately in the gastrointestinal tract and circulate to certain areas of the body. Thus, the use of the quick and simple HPLC method will allow researchers to verify that the amount of fenbendazole listed on the product labels is accurate. This will be important in future research utilizing fenbendazole as an experimental tool. fenben lab fenbendazol