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|Chemical and physical data|
|3D model (JSmol)|
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Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including: giardia, roundworms, hookworms, whipworms, the tapeworm genus Taenia (but not effective against Dipylidium caninum, a common dog tapeworm), pinworms, aelurostrongylus, paragonimiasis, strongyles, and strongyloides that can be administered to sheep, cattle, horses, fish, dogs, cats, rabbits, and seals.
Fenbendazole is being investigated for use as a cancer treatment in humans.
Drug interactions may occur if salicylanilides such as dibromsalan and niclosamide are co-administered. Abortions in cattle and death in sheep have been reported after using these medications together. Abortions in domestic ruminants have been associated with concurrent use of anti-trematode therapeutic agents.
Despite being widely used as a dewormer in many species, toxicity has been reported. Birds (storks, pink pelicans, vultures, pigeons and doves) and reptiles (vipers, turtles and tortoises) have shown toxicity associated with bone marrow suppression, intestinal crypt cell necrosis, and distal villi sloughing.
Fenbendazole is metabolized in the liver to oxfendazole, which is anthelmintic too; oxfendazole partially gets reduced back to fenbendazole in the liver and rumen. Also, fenbendazole itself is an active metabolite of another anthelmintic drug, febantel.