RENAL EXCRETION OF SULFAMERAZINE 1

Abstract

The addition of a methyl group to the pyrimidine ring of sulfadiazine to form sulfamerazine results in a compound that has a very low overall renal excretion rate. This is the result of extensive reabsorption by the renal tubules and binding on plasma proteins. The N4-acetyl derivative of sulfamerazine (which is presumably its conjugated form) is secreted rather than reabsorbed by the renal tubules. The low overall excretion rate of sulfamerazine has 2 distinct therapeutic advantages. First, relatively infrequent and small doses are required to maintain any given plasma conc. Second, the urine conc. of the drug at any given plasma level is less than that of other sulfonamides in current use. Such a circumstance should minimize the renal hazard of sulfonamide therapy, but additional factors such as solubility, urine flow, and pH may be expected to operate in this respect. An increase in the excretion rate of sulfamerazine accompanies augmented electrolyte elimination. This occurs when the electrolyte excretion is increased by a variety of means. The renal excretion of sulfamerazine does not appear to be simply related to the rate of urine formation. Indirect evidence suggests that sulfamerazine is reabsorbed by an active transport system in the renal tubules but this has not yet been directly demonstrated.