Pharmacotherapeutic group: Anthelmintics, benzimidazoles and related substances, fenbendazole.
ATCvet Code: QP52AC13
Pharmacodynamic properties
Fenbendazole is an anthelmintic belonging to the benzimidazole-carbamate group. It acts by interfering with the energy metabolism of the nematode.
Fenbendazole inhibits the polymerisation of tubulin to microtubules. This interferes with essential structural and functional properties of the cells of helminths, such as formation of cytoskeleton, formation of the mitotic spindle and the uptake and intracellular transport of nutrients and metabolic products.
Pharmacokinetic properties
Fenbendazole is only partly absorbed after oral administration and is then metabolised in the liver. Body clearance of fenbendazole in serum after intravenous administration to pigs at a dose rate of 1 mg/kg was 1.36 L/h/kg, volume of distribution at steady state was 3.35 L/kg and the mean residence time was 2.63 hours. After oral administration at a dose rate of 5 mg/kg the peak plasma concentration of fenbendazole was 0.07µg/ml, the Tmax was 3.75 hours and the mean residence time was 15.15 hours. The bioavailability was 27.1 %. Oxfendazole was the major plasma metabolite i.e 2/3 of the total AUC.
Fenbendazole and its metabolites are distributed throughout the body and high concentrations can be found in the liver.
The elimination of fenbendazole and its metabolites occurs primarily via the faeces (>90%) and to a small extent in the urine and milk.
Fenbendazole is metabolised to its sulphoxide, then to sulphone and amines.