The metabolism and elimination of S-carboxymethyl-L-cysteine in man.

The metabolism of 14C- and 35S-labeled S-carboxymethylcysteine (SCMC) has been compared. The majority of the dose appeared in urine in the first 24 hr; no activity was detectable in feces. Use of 25S-labeled compound gave small amounts of inorganic 35S-sulfate, whereas 14C-labeled material was degraded to give some [14C]urea. Peak excretion of the parent compound occurred first after administration of SCMC; metabolites requiring one chemical modification for their formation were maximally excreted 1-4 hr after the dose and those involving more metabolic processes appeared later (4-8 hr).