Fenbendazole


Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including: giardia, roundworms, hookworms, whipworms, the tapeworm genus Taenia, pinworms, aelurostrongylus, paragonimiasis, strongyles, and strongyloides that can be administered to sheep, cattle, horses, fish, dogs, cats, rabbits, and seals.

Drug interactions

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.

Toxicity

Despite being widely used as a dewormer in many species, toxicity has been reported. Birds and reptiles have shown toxicity associated with bone marrow suppression, intestinal crypt cell necrosis, and distal villi sloughing.
Fenbendazole is poorly absorbed from the gastrointestinal tract in most species. The in laboratory animals exceeds 10 g/kg when administered orally.

Metabolism

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.