AUTOMATED MICROANALYSIS OF OXCARBAZEPINE AND ITS MONOHYDROXY AND TRANSDIOL METABOLITES IN PLASMA BY LIQUID-CHROMATOGRAPHY

An automated high-performance liquid chromatographic method for the simultaneous determination of oxcarbazepine and its monohydroxy and transdiol metabolites in plasma is described. 5,6-Dihydro-11-oxo-11H-dibenz[b,e]azepine-5-carboxamide was used as internal standard. Liquid-solid extraction from plasma (100 mu l) on 50 mg Bond-Elut C-18 cartridges was automatically performed by the Automatic Sample Preparation with Extraction Columns (ASPEC) system. A reversed-phase column (ODS Hypersil, 3 mu m particle size, 4 cm x 4.6 mm I.D.) was used with acetonitrile-methanol-0.01 M potassium dihydrogenphosphate as mobile phase. The eluted compounds were detected at 210 nm. The limit of quantitation was 0.2 mu mol/l for oxcarbazepine and 0.1 mu mol/l for its metabolites. No interference with concomitantly administered anti-epileptic drugs such as phenobarbital, phenytoin, valproic acid or carbamazepine, was found.