ISOLATION AND IDENTIFICATION OF 3-CARBAMOYLOXY-2-PHENYLPROPIONIC ACIDAS A MAJOR HUMAN URINARY METABOLITE OF FELBAMATE

A new metabolite of felbamate, isolated from the polar metabolite frac tion of a human urine sample, was identified as 3-carbamoyloxy-2-pheny lpropionic acid (CPPA) by electron impact and CI/MS of the methyl este r in the isolated fraction. Its presence in the unconjugated free form in two different human urine samples was confirmed by HPLC comparison of retention times with authentic synthetic CPPA and by on-line negat ive ion HPLC thermospray tandem mass spectrometric techniques. The amo unt of CPPA in 0-4 hr postdose human urine was estimated to be approxi mately 12% of the drug-derived substances present in the urine. Some C PPA was also found to be present in dog urine.