The incidence of Zolpidem use in suspected DUI drivers in Miami-Dade Florida: a comparative study using immunalysis Zolpidem ELISA KIT and gas chromatography-mass spectrometry screening.

In 1993, Zolpidem (Ambien), a non-benzodiazepine hypnotic agent, was approved for use in the United States for the short-term treatment of insomnia. Zolpidem has a rapid onset of action and short elimination half-life, rendering it ideal as a sleep aid. The objective of this study was to evaluate, and retrospectively compare, the use of the Immunalysis ELISA kit and gas chromatograpy-mass spectrometry (GC-MS) to screen blood/urine specimens for zolpidem. In addition, results for the incidence of zolpidem in suspected DUI drivers in 2007 are compared to previous years' data. The ELISA kit was evaluated for cross-reactivity with zaleplon and zopiclone and zolpidem metabolite I. Urine samples (n = 100) and blood samples (n = 100) were selected from specimens received into the DUI laboratory in 2007 and were screened via the Immunalysis Zolpidem ELISA kit and on GC-MS in full EI scan mode following an alkaline liquid-liquid extraction. Results show 5% of the urine and blood samples screened positive for zolpidem using the ELISA kits, and all 5% confirmed positive for zolpidem using GC-MS. The ELISA kit demonstrated no cross-reactivity to zaleplon or zopiclone at a spiked urine concentration of 1000 ng/mL. Ten cases of suspected DUI drivers in 2007 confirmed positive for zolpidem by ELISA and GC-MS in blood/urine, a higher incidence rate than in the previous years. Because of the low percentage elimination of the parent compound in urine, a screening method for the detection of the main metabolite of zolpidem may be needed for better detection of drug impairment driving due to zolpidem.