Ruminant species, biotransformation

Albendazole and fenbendazole, prochiral sulphide benzimidazole anthelmintics, are metabolically converted (sulphoxidation) to the corresponding active sulphoxide metabolites, each of which exists in the plasma as two enantiomers. Sulphoxide benzimidazoles have a chiral centre around the sulphur atom in their molecules. The sulphoxide metabolites (enantiomers) are irreversibly metabolized (sulphonation) to inactive sulphones. This pathway of hepatic biotransformation has been shown to occur both in ruminant (sheep, goats, cattle) and monogastric (man, dogs, rats) species (Delatour et al., 1991b,... 

Wachenheim DE, Blythe LL, Craig AM. Characterization of rumen bacterial pyrrolizidine alkaloid biotransformation in ruminants of various species. Vet Hum Toxicol 34 513-516, 1992. 

---