Modification of the EMIT tox benzodiazepine assay for screening of alprazolam in serum.

Abstract

Alprazolam (Xanax) is a relatively new triazolobenzodiazepine which is anxiolytic in man and is also prescribed in the treatment of panic attacks. The objective of this study was to optimize the reactivity of the EMIT tox serum benzodiazepine assay for toxicologic screening of alprazolam. The standard EMIT procedure was extensively modified so that therapeutic concentrations of alprazolam could be detected. Modifications for Methods A and B included a single dilution of specimens, increasing incubation temperature to 37 degrees C, dilution of Reagents A and B, and increasing specimen volume to 100 microL. Method B also included supplementing Reagent A with additional glucose-6-phosphate and beta-nicotinamide adenine dinucleotide. Using serum standards, the modified EMIT assays have detection limits of approximately 25 ng/mL (Method A) and 20 ng/mL (Method B). The patient specimens analyzed were considered positive by Method B and 24/28 positive by Method A. All 28 patient specimens tested by Method B were confirmed positive by gas chromatography/electron capture detection. The day-to-day precision of both methods was less than 2% CV with diluted EMIT calibrators (N = 6). In conclusion, the modified EMIT assay can be used to screen for alprazolam in serum at therapeutic concentrations.