Tritiation of tylosin and metabolic study in the rat.

Tritiated antibiotic tylosin was prepared by aqueous exchange, purified, then stabilized under phosphate form. After oral administration to rats, the balance study showed the following distribution: urine 10%, feces 46%. Urinary and fecal metabolites were identified as tylosin and desmycosin; 65 % of the urinary radioactivity was tritiated water. The elimination is biphasic. 3H-Tissue accumulation and depletion have been studied; 80~90%of the recovered radioactivity was associated to tritiated water. In six tissues including blood, muscle and liver, tissue residue levels were established within 20 days at 0.1 ~0.3 ppm; depletion isslow.