Cd. Thompson et al., Quantification in patient urine samples of felbamate and three metabolites: Acid carbamate and two mercapturic acids, EPILEPSIA, 40(6), 1999, pp. 769-776
Purpose: Previously we proposed and provided evidence for the metabolic pat
hway of felbamate (FBM), which leads to the reactive metabolite, 3-carbamoy
l-2-phenylpropionaldehyde. This aldehyde carbamate was suggested to be the
reactive intermediate in the oxidation of 2-phenyl-1,3-propanediol monocarb
amate to the major human metabolite 3-carbamoyl-2-phenylpropionic acid. In
addition, the aldehyde carbamate was found to undergo spontaneous eliminati
on to 2-phenylpropenal, commonly known as atropaldehyde. Moreover, atropald
ehyde was proposed to play a role in the development of toxicity during FBM
therapy. Evidence for atropaldehyde formation in vivo was reported with th
e identification of modified N-acetyl-cysteine conjugates of atropaldehyde
in both human and rat urine after FBM administration. Identification of the
atropaldehyde-derived mercapturic acids in urine after FBM administration
is consistent with the hypothesis that atropaldehyde is formed in vivo and
that it reacts with thiol nucleophiles. Based on the hypothesis that the po
tential for toxicity will correlate to the amount of atropaldehyde formed,
we sought to develop an analytic method that would quantify the amount of r
elevant metabolites excreted in patient urine.
Methods: We summarize the results of an LC/MS method used to quantify FBM,
3-carbamoyl-2-phenylpropionic acid and two atropaldehyde-derived mercapturi
c acids in the patient population.
Results: Analysis was performed on 31 patients undergoing FBM therapy. The
absolute quantities of FBM and three metabolites were measured.
Conclusions: This method demonstrated sufficient precision for the identifi
cation of patients exhibiting "abnormal" levels of atropaldehyde conjugates
and may hold potential for patient monitoring.