The In Vitro and In Vivo Study of the Pharmacokinetics and Metabolism of Anthelmintics in Equidae

Fenbendazole is a thio-substituted benzimidazole used in the treatment of helminths of domestic animals. It has poor water solubility and is rapidly biotransformed and eliminated from the animals' body. These features are common to the 'newer' benzimidazoles and pose a serious constraint on their efficacy, especially in the equine species with short gut transit time. Anthelmintic activity of the benzimidazoles is related to the period of time the parasite is exposed to effective concentrations of the active compounds (i.e. the parent sulphide and the sulphoxide metabolite), consequently residence time of the active compound is important