The effect of immunization with protein-sulphanilic acid conjugate on sulphanilic acid disposition in the rat.

Rats were immunized with bovine gamma-globulin-sulphanilic acid conjugate and the plasma concentration of sulphanilic acid examined after an intravenous injection of this drug. There was a significant increase in plasma half-life and AUC and a significant decrease in clearance of sulphanilic acid in the immunized rats compared with the control. In the immunized rats, binding of sulphanilic acid to macromolecules in serum, determined by ultrafiltration, decreased with increase of sulphanilic acid concentration. At low concentrations, there was a significant increase in % binding of the drug in the serum of immunized rats compared with controls. There was also a significant reduction in urinary excretion of total drug in the immunized rats compared with controls. These findings suggest that sulphanilic acid-specific antibodies in the serum of immunized animals bind [14C]sulphanilic acid, giving rise to higher serum levels thereby making it unavailable for normal excretory processes.