DEPLETION OF DIETARY SULPHAMONOMETHOXINE AND SULFADIMETHOXINE FROM VARIOUS TISSUES OF LAYING HENS

1. Sulphamonomethoxine (SMM) or sulphadimethoxine (SDM) was fed to lay ing hens at 400 mg/kg diet for 5 successive days. After withdrawal of the drugs, contents (mg/kg) of SMM and SDM in the blood, kidney, liver , ovary, muscle and adipose tissue were determined by HPLC. 2. The dis appearance of dietary SMM and SDM from the tissues of laying hens was rapid and, except for the liver, was very similar in all tissues. 3. A common biological half-life (t(1/2)) of SMM in the above 6 tissues wa s estimated to be 5.2 h. The t(1/2) of SDM in the liver was 6.9 h, sig nificantly longer than that of 4.4 h in the other 5 tissues. The value s were much shorter than t(1/2) (reported elsewhere) for other drugs. 4. Comparing the data found in this study with those obtained from pre vious papers, the depletion velocities of SMM and SDM from the hen's b ody were much faster than those from albumen in egg. The reason for th is is probably related to the longer time period over which albumen fo rmation occurs.