Carbamazepine determination in saliva of children: enzyme immunoassay (EMIT) versus high pressure liquid chromatography.

Concentrations of carbamazepine (CBZ) in salivary specimens from epileptic children receiving CBZ monotherapy were measured by EMIT and high pressure liquid chromatography (HPLC). A highly significant linear correlation was obtained between the two methods. Statistical analysis indicated significantly greater CBZ concentrations by EMIT than by HPLC, probably due to interference in the EMIT assay by the main metabolite, carbamazepine-10,11-epoxide (EP). For patients on monotherapy this difference would appear not to be great enough to lead to misinterpretation of the result in clinical practice. However, with combined therapy, interference by EP in the salivary measurement of CBZ by EMIT may well become a problem. The main advantage of HPLC is that it is specific for CBZ; also, it can separate and quantify EP concurrently, which may be beneficial if EP is shown to have antiepileptic activity in man. In this study of epileptic children on monotherapy, the salivary concentration ratio EP/CBZ showed large variations both within and between patients, with a mean of 31.6% and an overall range of 6.8-67.1%.