9-Hydroxymethyl-10-carbamoylacridan in human serum is one of the major metabolites of carbamazepine.

In sera of 29 patients under the chronic administration of carbamazepine (CBZ, dose: 10.9 +/- 4.3 mg/kg/day), a ring-contracted metabolite of CBZ was detected at a relatively higher concentration of 0.57 +/- 0.30 mu g/ml (mean +/- S.D.) by high-performance liquid chromatogaphic assay. The structure of the metabolite was identified as 9-hydroxymethyl-10-carbamoylacridan (HMCA) by the liquid chromatography-mass spectral examination, and also by comparison with the authentic sample. Although HMCA was already reported in a few papers as a minor metabolite of CBZ in human urine, any reliable report for the determination of HMCA in human blood has never been published. Our results show that HMCA is one of the major metabolites of CBZ.