Fenbendazole (Hoechst brand names Panacur and Safe-Guard, Intervet Panacur and Panacur Rabbit) is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including: giardia, roundworms, hookworms, whipworms, the Taenia genus of tapeworms (but not effective against Dipylidium caninum, a common dog tapeworm), pinworms, aelurostrongylus, paragonimiasis, strongyles and strongyloides and can be administered to sheep, cattle, horses, fish, dogs, cats, rabbits and seals. Drug interactions may occur if salicylanilides like dibromsalan and niclosamide are co-adminstered. Abortions in cattle and death in sheep have been reported.[1]


  • Toxicity 1
  • Synthesis 2
  • Metabolism 3
  • See also 4
  • References 5
  • External links 6


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. Abortions in domestic ruminants have been associated with concurrent use of anti-trematode therapeutic agents.

Fenbendazole is poorly absorbed from the gastrointestinal tract in most species. The LD50 in laboratory animals exceeds 10 g/kg when administered orally.[1]


Fenbendazole synthesis[2][3]


It gets metabolized in the liver to oxfendazole, which is anthelmintic too; oxfendazole partially gets reduced back to fenbendazole in the liver and rumen.[4][5] Also, fenbendazole itself is an active metabolite of another anthelmintic drug, febantel.[6]

See also


  1. ^ a b Plumb's Veterinary Drug Handbook, Fifth Edition, 2005.
  2. ^ H. Loewe et al., DE 2164690 ; eidem, U.S. Patent 3,954,791 (1973, 1976 both to Hoechst)
  3. ^ C. Baeder et al., Experientia 30, 753 (1974).
  4. ^
  5. ^
  6. ^

External links

  • PetPlace Drug Library
  • 3Dchem.com – Chemical structure