ATCvet code: QP52AC13.
Pharmacodynamic properties
Fenbendazole is an anthelmintic belonging to the benzimidazole-carbamates group. It acts by interfering in the energy metabolism of the nematode.
The anthelmintic affects both adult and immature stages of gastrointestinal and respiratory nematodes. This anthelmintic efficacy is based on inhibition of the polymerisation of tubulin to microtubuli.
Pharmacokinetic properties
The veterinary medicinal product remains in the reticulum or rumen and disintegrates over time with an increased loss of rings. The release rate of the intraruminal device ranges from 0.23 - 1.04 mg fenbendazole/kg/day. Fenbendazole is only partly absorbed from the gastrointestinal tract.
Fenbendazole is metabolised mainly by enzymes of the cytochrome P -450 system in the liver. The major oxidative metabolite is fenbendazole sulfoxide which is further metabolised to fenbendazole sulfone. Other metabolites are p-hydroxyfenbendazole and fenbendazole amine, the major urinary metabolite.
Fenbendazole and its metabolites are distributed throughout the body and high concentrations can be found in the liver.
Fenbendazole and its metabolites are undetectable in the plasma at 127 - 131 days after administration.
The elimination of fenbendazole and its metabolites occurs primarily via the faeces and to a small extent in the urine and milk.
Environmental properties
Fenbendazole is toxic to fish and other aquatic organisms.