HIGH-SPEED LIQUID-CHROMATOGRAPHIC METHOD FOR THE MONITORING OF CARBAMAZEPINE AND ITS ACTIVE METABOLITE, CARBAMAZEPINE-10,11-EPOXIDE, IN HUMAN PLASMA

The assays of antiepileptic drugs, which are performed by central labo ratories in Phase II and III clinical trials, require both a very fast turn-around time and a suitable specificity. In order to decrease the run time and to keep the powerful specificity of the liquid chromatog raphy (HPLC), the use of a reversed-phase 1.5 mu m monosized non-porou s silicon dioxide microspheres column instead of regular columns conta ining spherical porous C-18 material was studied. The determination of carbamazepine (CBZ) and its active metabolite, carbamazepine-10,11-ep oxide (CBZ-E), in human plasma or serum was chosen to demonstrate the utility of these columns. As a prerequisite of this work, no modificat ion of a regular HPLC system was allowed. The samples were prepared in autosampler vials by protein precipitation with acetonitrile, followe d by a quick centrifugation. Without any change to a conventional HPLC system, CBZ and CBZ-E are well separated in less than 2.5 min using a Kovasil MS C-14 column. No interference was observed with endogenous compounds and with nine antiepileptic drugs commonly prescribed as co- medication, and their metabolites. Due to the very low specific surfac e area of the packing, the required organic modifier volume per chroma tographic run was decreased by a factor of 25. The method was validate d. The developed method is well suited for the determination of CBZ an d CBZ-E in clinical trials. It can be easily adapted to the monitoring of other antiepileptic drugs. No modification of a regular HPLC syste m was required.