Evaluation of the EMIT Tox enzyme immunoassay for toxicological analysis of benzodiazepines in serum

Evaluation of Emit tox benzodiazepine and barbiturate assays on the Vitalab Viva analyser and FPIA on the Abbott ADx analyser

We evaluated the performance of the Emit tox benzodiazepine and barbiturate assays (Dade Behring) and fluorescence polarisation immunoassay (FPIA) (Abbott) for use with serum determinations in preliminary therapeutic drug monitoring or acute drug intoxication detection. Performance, as indicated by CVs, of the Emit tox benzodiazepine and barbiturate assays and FPIA showed that both immunochemical techniques are precise and have good reproducibility. For within-run studies, results from benzodiazepine determinations showed maximum CV values of 1.91% for the Emit method and 2.65% for FPIA; results from barbiturate determinations showed maximum CV values of 2.01% for the Emit method and 1.89% for FPIA. For between-run studies, results from benzodiazepine determinations showed maximum CV values of 1.79% for the Emit method and 1.12% for FPIA; results from barbiturate determinations showed maximum CV values of 2.09% for the Emit method and 2.02% for FPIA.

Monitoring of benzodiazepines (clobazam, diazepam and their main active metabolites) in human plasma by column-switching high-performance liquid chromatography

A column-switching high-performance liquid chromatographic method for the simultaneous determination of clobazam, diazepam and their main metabolites in human plasma is described. A 200-microliters plasma sample was directly injected into a precolumn filled with TSK-gel PW. After a washing step with potassium phosphate buffer, the retained substances were backflushed into a reversed-phase column with a mobile phase of acetonitrile-phosphate buffer-diethylamine. Various drugs frequently co-administered with clobazam or diazepam do not interfere with the determination.

Monoclonal antibodies to benzodiazepines

Four hybridoma lines secreting monoclonal antibodies to benzodiazepines were produced after BALB/c mice were immunized with a benzodiazepine-bovine serum albumin conjugate. The monoclonal antibodies were purified from ascites fluids, and their binding affinities for benzodiazepines and other benzodiazepine receptor ligands were determined. These antibodies have very high binding affinities for diazepam, flunitrazepam, Ro5-4864, Ro5-3453, Ro11-6896, and Ro5-3438 (the KD values are in the 10(-9) M range). However, these antibodies have low affinities for the benzodiazepine receptor inverse agonists (beta-carbolines) and antagonists (Ro15-1788 and CGS-8216).

Determination of clobazam, N-desmethylclobazam and their hydroxy metabolites in plasma and urine by high-performance liquid chromatography

Owing to the pharmacological and clinical importance of the determination of plasma and urine levels of the hydroxy metabolites of clobazam and N-desmethylclobazam in healthy volunteers and in epileptic patients, a high-performance liquid chromatographic (HPLC) method was developed that permits the determination of all these compounds in the same plasma or urine sample. The method involved ether extraction at pH 13 with diazepam as internal standard for the measurement of clobazam and N-desmethylcobazam, followed by ether extraction at pH 9 with nitrazepam as internal standard for the measurement of the hydroxy derivatives. The limit of detection was about 10-20 ng/ml for each of these compounds. Applications to patients were limited by chromatographic interferences between the hydroxy metabolites and some medications currently associated with clobazam in the treatment of epilepsy. The only interference in clobazam and N-desmethylclobazam analysis was from N-desmethyldiazepam. Despite these inconveniences, this HPLC procedure appears to be the only available method for the simultaneous quantification of clobazam and its three main metabolites.