Distribution of total 14C residue in egg yolk, albumen, and tissues following oral [14C]sulfamethazine administration to hens

The distribution of total C-14 residues was studied in egg yolk and albumen after administration of either single or multiple oral dosages of [C-14]sulfamethazine (SMZ). One day after a single dose of [C-14]SMZ (121 mg of sulfamethazine, 2.42 x 10(7) dpm), the 14C residue concentration peaked in egg albumen and egg yolk with the concentration in the former > 4-fold greater than in the latter. Three days postdose, the C-14 residue concentration in the yolk was similar to7-fold higher than in the egg albumen. A multiple dose of [C-14]SMZ containing sulfamethazine mass equivalent of an average therapeutic dose (282 mg, 2.9 x 10(7) dpm) for chickens was also administered orally for six consecutive days to hens. A significantly reduced level of egg production was observed during the medication, and most of the hens stopped laying eggs after the last dose. The C-14 residue concentrations peaked on the last day (sixth) of medication in egg albumen and yolk. The C-14 residue concentrations were also measured in liver, muscle, blood, and plasma of chickens sacrificed at 1, 24, 48, and 72 h after the last dose. Highest concentrations of C-14 residue were accumulated in Liver followed by, in decreasing order, blood, plasma, and muscle.