Simultaneous assay of felbamate plus carbamazepine, phenytoin, and their metabolites by liquid chromatography with mobile phase optimization.
Felbamate is an investigational antiepileptic drug (AED) in clinical trials. A high-performance liquid chromatographic method for the simultaneous analysis of felbamate, phenytoin (PHT), 5-(p-hydroxyphenyl)-5-phenylhydantoin, carbamazepine (CBZ), carbamazepine-10,11-epoxide, and carbamazepine-10,11-diol in serum was developed by a mobile phase optimization technique. Capacity factors for the compounds of interest and 12 other AEDs and metabolites were determined with mixtures of methanol, acetonitrile, or tetrahydrofuran and a 0.01 M ammonium phosphate buffer, pH 6.5, on a reversed-phase C8 column. An optimized mobile phase composition was determined that could separate the compounds of interest and three internal standards in less than 15 min. Serum was extracted with CH2Cl2/ethyl acetate (2:1) after addition of three internal standards. The method was validated for within-day and between-day precision and accuracy for the six compounds. Coefficients of variation were generally less than 10% at all concentrations and less than 5% in the typical therapeutic range for each compound. The lower limit of detection was estimated at 0.2 micrograms/ml for CBZ and its metabolites and 0.5 micrograms/ml for felbamate and PHT. For felbamate, the lowest point on the standard curve was 1.88 micrograms/ml with a between-day variability of 10.3%. The assay was used to determine the serum concentrations of PHT and CBZ and its metabolites in a subject before, during, and after felbamate therapy.
Remmel
R P
RP
Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis 55455.
Miller
S A
SA
Graves
N M
NM
D002220:Carbamazepine / Q000031:analogs & derivatives / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D000078328:Felbamate; D006801:Humans; D048448:Phenylcarbamates; D010672:Phenytoin / Q000031:analogs & derivatives / Q000097:blood*; D011409:Propylene Glycols / Q000097:blood*
D048448:Phenylcarbamates; D011409:Propylene Glycols; C027364:5-(3-hydroxyphenyl)-5-phenylhydantoin; D002220:Carbamazepine; D010672:Phenytoin; C012227:carbamazepine epoxide; D000078328:Felbamate