Abstract

Renal clearances of sulfamerazine, sulfadiazine, sulfapyridine, sulfathiazole, acetyl sulfamerazine, acetyl sulfadiazine, and acetyl sulfathiazole have been measured in men and compared with the simultaneously determined clearance of inulin. Results were corrected for sulfonamide unavailable for excretion due to combination with plasma protein.

Sulfathiazole differed from the other three sulfonamides in showing a mean clearance averaging 87 per cent of the inulin clearance. Thus, reabsorption by the tubules was of minor significance.

The clearance of sulfamerazine averaged 20 per cent, sulfapyridine 28 per cent, and sulfadiazine 31 per cent of the inulin clearance, indicating that these compounds are extensively reabsorbed by the tubules.

Acetylated sulfonamides have higher clearances than the free forms. Acetyl sulfamerazine and acetyl sulfathiazole appear to be excreted by a combination of glomerular filtration and tubular secretion. Acetyl sulfadiazine shows a similar behavior, but the filtration-reabsorption pathway seems to be the predominant one.

Four subjects with moderately impaired renal function showed the same ratio of sulfamerazine to inulin clearance as those with normal renal function.

The temporary diminution in urea clearance previously observed during therapeutic administration of sulfonamides occurs also in normal individuals receiving comparable amounts of these drugs.