High-performance liquid chromatography-tandem mass spectrometry method for simultaneous quantification of carbamazepine, oxcarbazepine, and their main metabolites in human serum.

BACKGROUND: Antiepileptic drug therapeutic regimens often need to be adjusted individually on the basis of serum assays. We aimed to develop a quantitative, fast, and sensitive liquid chromatography-tandem mass spectrometry method to simultaneously analyze carbamazepine, oxcarbazepine, and the 10-11 epoxide carbamazepine and 10-hydroxy carbazepine (mono-hydroxy derivative, 10,11-Dihydro-10-hydroxycarbamazepine) metabolites, in human serum. METHODS: Serum samples were deproteinized by acetonitrile spiked with dansyl-norvaline as internal standard. Compounds were separated on a reversed-phase high-performance liquid chromatography over a total run time of 10 minutes. Serum concentrations were then measured by means of a triple quadrupole tandem mass spectrometer, set up in positive mode and multiple reaction monitoring. RESULTS: Calibration curves (0.08-50 mcg/mL for carbamazepine and 10,11-dihydro-10-hydroxycarbamazepine; 0.03-20 mcg/mL for oxcarbazepine and epoxide carbamazepine) were linear, with a mean correlation coefficient >0.999. Both the intra- and interassay imprecision and inaccuracy were within 10%. The absolute recovery ranged from 98% to 103% for all analytes. CONCLUSIONS: The method requires minimal sample preparation. Volume of the sample is lower and run time shorter than required by previous published liquid chromatography-tandem mass spectrometry methods. Results are accurate. The method seems, therefore, to be reliable and economically suitable for routine analysis of antiepileptic drugs monitoring in clinical settings.