Sulfanilamide, sulfathiazole, sulfisomezole and their five biotransformed products were applied to renal clearance experiments in dogs and protein binding experiments to dog plasma protein in order to elucidate their renal excretion behaviors.
Clearance ratio of sulfisomezole is considerably low compared with that of other two sulfonamides.
Biotransformation of sulfisomezole to sulfisomezole-N4-acetate and sulfisomezole-N¹-glucuronide led to remarkable rise of clearance ratio.
N⁴-acetylation of sulfathiazole rather reduced clearance ratio compared with the original sulfonamide. On the contrary, N⁴-acetylation of sulfanilamide lead to rise of clearance ratio, in spite of high clearance ratio of sulfanilamide.
N⁴-acetylated products of the three sulfonamides are considerably secreted through proximal tubule. Proximal tubular secretion of sulfisomezole-N¹-glucuronide is insufficient.
N⁴-acetylation of the three sulfonamides increased affinity for dog plasma protein. On the other hand, reduced affinity of sulfisomezole-N¹-glucuronide for dog plasma protein was observed.
Furthermore, correlation between renal excretion and biotransformation of several sulfonamides was extensively discussed.