Evaluation of proposed sulphoxidation pathways of carbocysteine in man by HPLC quantification.
A quantitative study has been made of the metabolism of S-carboxymethyl-L-cysteine (CMC) and its sulphoxides in volunteers by HPLC. Precolumn derivatization was applied prior to gradient reversed phase HPLC separation and fluorescence detection. For CMC and its metabolites containing a primary amino group the reagent 9-fluorenylmethylchloroformate was used. The other metabolites of CMC were derivatized at their carboxylic group with 1-pyrenyldiazomethane to give stable fluorescent products. Urine samples were collected for 8 h after oral administration of 1.125 g CMC to 33 healthy volunteers. Elimination of CMC in urine as sulphoxides did not account for more than 1% of the dose in any of the volunteers. Thus, CMC-sulphoxide metabolites are not quantitatively important. Recovery of the original substance in 8-hour urines ranged from 10 to 30% and a further 2 to 20% was recovered as the metabolite thiodiglycolic acid. Oral doses of 0.19, 1.125, and 2.25 g CMC in a second group of 12 healthy volunteers did not reveal dose dependence of the urinary excretion of the sulphoxides or of thiodiglycolic acid. Serum concentration-time-curves of CMC, (S)- and (R)-CMC sulphoxide were measured in a group of 9 healthy volunteers. The CMC sulphoxides in serum reached 1.5% of the parent substance after 4 hours. The ratio of CMC to its sulphoxide metabolites was similar in serum and urine. Pharmacogenetic polymorphism of sulphoxidation was not confirmed by the specific HPLC methods used.
Brockmöller
J
J
Institut für Klinische Pharmakologie, Universitätsklinikum Steglitz, Freie Universität Berlin, FRG.
Staffeldt
B
B
Roots
I
I
D000284:Administration, Oral; D000328:Adult; D002233:Carbocysteine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013454:Sulfoxides / Q000652:urine*
D013454:Sulfoxides; D002233:Carbocysteine