[Metabolism-embryotoxicity relationship of febantel in the rat and the sheep].

The metabolism of febantel has been investigated in the rat and the sheep. The general pathway seems to be similar in both species: ten urinary metabolites are the result of cyclisation, oxidation and/or hydrolysis process. Using synthetic samples, the embryotoxic study of all individual metabolites has been performed in the rat. Unchanged febantel and two other metabolites are responsible for teratogenic effects. A four steps toxogenic pathway is described which finally leads to the ultimate known teratogen: methyl (5-(phenylsulfinyl)-1H-benzimidazole-2-yl) carbamate. Metabolic similarities with other anthelmintics and residual consequences are discussed.