The metabolism ofS-carboxymethyl-L-cysteine in man: isolation of an ester glucuronic acid conjugate from urine

A conjugate isolated from urine of human volunteers after an oral dose of S-carboxymethyl-L-cysteine was characterized as a carboxylic acid ester glucuronide. Of the 166 volunteers investigated, 61 gave no detectable drug glucuronide (less than 0.5% administered dose); the remaining 105 showed a unimodal distribution of drug glucuronide excretion accounting for 0.5-11.5% (mean 4.1%, median 3.4%) of the total dose recovered in the 0-8 h urine. No significant variation in subject age, sex or urinary pH was observed between the two groups, but those not excreting urinary glucuronide had significantly higher 0-8 h urine volumes (P less than 0.001), although notable exceptions occurred.