Urinary screening for midazolam and its major metabolites with the Abbott ADx and TDx analyzers and the EMIT d.a.u. benzodiazepine assay with confirmation by GC/MS

Midazolam is a short-acting 1,4-imidazole benzodiazepine with sedative-hypnotic, anxiolytic, and amnestic properties. It is administered orally for sleeping disorders and intravenously for sedation during surgery. This drug has a short half-life (1.5-3.5 h), with less than 1% of a midazolam dose being excreted unchanged. The major urinary metabolite is α-hydroxy midazolam glucuronide. The objective of this study was to characterize the reactivity of midazolam and its two major metabolites in the EMIT® d.a.u.(TM) benzodiazepine assay and in the Abbott TDx® and ADx® urine benzodiazepine assays. Midazolam and α-OH midazolam gave an equivalent response to the EMIT low calibrator at 200 ng/mL. On both Abbott analyzers, midazolam and α-OH midazolam gave an equivalent net polarization at 500 ng/mL to the Abbott low control. All three screening assays were positive in all of 21 random urine specimens collected from midazolam-treated patients. Confirmation testing was performed by analyzing for α-OH midazolam after enzymatic hydrolysis and formation of a TMS derivative for GC/MS. All urine specimens were confirmed positive for α-OH midazolam. In conclusion, all three immunoassay screening assays are acceptable for detecting the presence of midazolam metabolites in urine.