Analysis of zolpidem in postmortem fluids and tissues using ultra-performance liquid chromatography-mass spectrometry

Zolpidem is a nonbenzodiazepine sedative hypnotic drug used for the short-term treatment of insomnia. While quite effective in producing sedation, zolpidem has potentially hazardous side effects when put in the context of complex tasks. Therefore, to more fully understand the postmortem concentrations of zolpidem, our laboratory has developed a sensitive method for the quantitation of zolpidem in biological specimens. Additionally, we have evaluated the distribution of zolpidem in various postmortem tissues and fluids from 10 aviation fatalities. This method incorporated a modified acetonitrile 'crash and shoot' extraction and a Waters Xevo TQ-S with an Acquity ultra-performance liquid chromatograph. The linear dynamic range was 0.4-800 ng/mL. The extraction efficiencies ranged from 78 to 87%, depending on the concentration. Postmortem blood zolpidem concentrations in these 10 cases ranged from 7.6 to 76.5 ng/mL. The highest concentrations of zolpidem present in each victim were found in the liver, spleen, lung and kidney tissues. Distribution coefficients for zolpidem were determined for each of the specimen types analyzed. These coefficients are expressed relative to the blood concentration in each case. This method proved to be simple, accurate and robust for the identification and quantitation of zolpidem in postmortem fluids and tissues.