Renal and mammary excretion of sulfadimidine in buffaloes

The renal and mammary excretion of sulfadimidine was investigated in 8 lactating buffaloes after intravenous administration. The results showed that sulfadimidine was bound to the proteins in plasma (39--59 per cent) and milk (5.5 per cent). The renal handling of sulfadimidine was influenced by the variations in the urinary pH and the concentration of non-protein-bound drug. From the results it is concluded that glomerular filtration, back diffusion and active tubular secretion are involved in the renal handling of sulfadimidine in buffaloes. The results of mammary excretion showed that sulfadimidine is excreted into milk of buffaloes in concentration lower than in plasma. The ratio between the concentration of sulfadimidine in milk and plasma increases when the pH of milk increases. The results are consistant with the theory that drugs are excreted through the mammary gland by passive diffusion.