Evaluation of the Enzyme Immunoassay for the Quantitation of Clonazepam Concentration in Plasma

We described the quantification of clonazepam in plasma using a semi-quantitative enzyme immunoassay reagent which rapidly identifies benzodiazepine overdosed in emergency cases. Since this reagent reacts with not only clonazepam but also several benzodiazepines and their metabolites, it is necessary to separate clonazepam from their metabolites before the measurement of its level. We excluded the interference of the clonazepam metabolites by using a sample preparation column.This method enabled the rapid quantification of clonazepam in plasma. The between-run precision was established by 8 replicated analyses during 20 days, and the coefficient of variation values ranged from 8.0 to 14.8%. Assay precision of this method were shown to be lesser than that of the high-performance liquid chromatography (HPLC) method. The lowest measurerable clonazepam concentration in plasma was about long/ml in the case of 0.5ml of sample used. Concentrations of plasma clonazepam in 29 patients determined by this method and HPLC method were compared and showed good correlations in the order of 0.917 in the linear regression analysis. We concluded that this method was sufficiently sensitive, convenient, and practically acceptable for the conventional therapeutic drug monitoring.