| Abstract: | 4-Epimers of tetracycline (TC) and chlortetracycline (CTC) were formed in vivo in laying hens and excreted in substantial amounts besides the residues of the administered parent compounds via the egg. The recent observation of isochlortetracycline (i-CTC) and its 4-epimer as being the principal metabolites in eggs after feeding CTC could be confirmed. The ratio of 4-epimer to parent compound of TC, CTC and i-CTC was lower in egg white and higher in yolk and did not change during medication with TC or CTC. Further, yet unidentified, in vivo formed metabolites were observed. |
