Adverse reactions (frequency and seriousness): None known.
Use during pregnancy, lactation or lay:
Chicken: Can be used during lay. The safety of the veterinary medicinal product has not been established in male birds. Therefore use in male birds only according to the benefit/risk assessment by the responsible veterinarian.
Pheasants: The safety of the product has not been evaluated in breeding pheasants. Therefore in these birds use only according to the benefit/risk assessment by the responsible veterinarian.
Interaction with other medicinal products and other forms of interaction: None known.
In the absence of compatibility studies, this veterinary medicinal product must not be mixed with other veterinary medicinal products.
Overdose (symptoms, emergency procedures, antidotes), if necessary
No adverse reactions have been observed at up to 5-fold the maximum recommended dose of 2 mg/kg body weight/day over 18 days in broilers (aged approximately 3 weeks) and up to a 40-fold overdose in pheasants (aged approximately 3 weeks). No adverse reactions have been observed at up to 3-fold the maximum recommended dose of 2 mg/kg body weight/day (chickens) in layers and breeders.
Pharmacotherapeutic group: Anthelmintics, benzimidazole derivatives – 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 the cytoskeleton, formation of the mitotic spindle and the uptake and intracellular transport of nutrients and metabolic products. Fenbendazole is active and has a dose dependent activity on Heterakis gallinarum (adult stages), Ascaridia galli (adult stages) and Capillaria obsignata (adult stages) in chickens, and activity against adult Heterakis gallinarum in pheasants.
Pharmacokinetic particulars
After oral administration fenbendazole is only partially absorbed. Following absorption, fenbendazole is rapidly metabolised in the liver mainly to its sulphoxide (oxfendazole) and further to its sulphone (oxfendazole sulphone). In chickens oxfendazole sulfone is the maincomponent detected in plasma, accounting for about 3/4 of the total AUC (i.e. the sum of the AUC for fenbendazole, oxfendazole and oxfendazole sulphone). Fenbendazole and its metabolites are distributed throughout the body, reaching highest concentrations in the liver. The elimination of fenbendazole and its metabolites occurs primarily via the faeces.