Cross-reactivity assessment of oxcarbazepine and its metabolites in the EMIT assay of carbamazepine plasma levels.

To study the possible cross-reactivity of trans-10, 11-dihydroxy-10, 11-dihydro-carbamazepine (DHCBZ), the diol metabolite of carbamazepine (CBZ), of oxcarbazepine (OCZ), and of its metabolites in the CBZ-enzyme multiplied immunoassay technique (EMIT), this technique was used to analyze sera spiked with CBZ, OCZ, DHCBZ, and 10-hydroxy-10, 11-dihydro-carbamazepine (HCBZ). OCZ and, to a lesser extent, HCBZ cross-reacted with the CBZ-EMIT reagents. However, from a clinical point of view, only HCBZ could significantly interfere in the quantitation of CBZ levels in the plasma of patients taking both CBZ and OCZ. There was no interference by DHCBZ.