Influence of diet on the pattern of gastrointestinal biotransformation of netobimin and albendazole sulphoxide in sheep

The in vitro biotransformation of the anthelmintic compounds, netobimin (NT B) pro-drug and albendazole sulphoxide (ABZSO), by ruminal fluid obtained f rom sheep fed either hay or concentrate-based diets was investigated. No me tabolic activity was observed in boiled samples of ruminal fluid, which con firms the importance of ruminal microflora in the metabolism of the xenobio tics under investigation. NTB pro-drug was efficiently biotransformed by ru minal fluid in vitro. Albendazole (ABZ) and its sulphoxide derivative were the metabolic products recovered. The thioether ABZ was formed by sulphored uction of ABZSO by ruminal fluid in vitro. A more efficient nitroreduction of NTB and sulphoreduction of ABZSO were observed for ruminal fluid collect ed from sheep fed the concentrate diet. The type of diet determines the com position and distribution of the microbial population in the rumen; this af fects the pattern of drug biotransformation in the gastrointestinal tract, which may impact on drug therapy.