| Antibiotics administered to food producing animals as feed additives or as anti-infectious veterinary drugs may give toxic residues for human health. These residues may either be identical to the initial substance or be present as metabolites with a modified structure and quite different pharmaco-toxicological properties. Study of the metabolism of tylosin, penicillin and chloramphenicol illustrates these aspects both for the methodology and in terms of toxicological implications for the consumer. The "residue" may have preserved the antibiotic properties of the initial compound, like in the case of tylosin residues. Through activation processes and especially binding with serum or microsome proteins it may also produce metabolites without any antibiotic activity, but with allergic or haemato-toxicological potentialities. In the study of these three antibiotics, emphasis was laid on the mechanisms responsible for the formation of these "high risk metabolites" and the role played by the gastro-intestinal microflora, the importance of the analytical tool used for detecting, determining and identifying them as well as the interest of the concept of bioavailability of these residues for the display of their toxic potentiality. |
